This PDF file contains the front matter associated with SPIE Proceedings Volume 12595 including the Title Page, Copyright information, Table of Contents, and Conference Committee Page.

A scheme for the photonic generation of Multi-band Reconfigurable Microwave Waveforms (MRMWs) is proposed and demonstrated based on dual-correlated chirped fiber combs. In the proposed system, the output of master laser is split into two paths, and then respectively coupled with another a single-frequency fiber laser and amplified for the generation of dual combs, which also acts as the reference frequency. During various formats wavelength sweeping operation, one of the single-frequency lasers can flexibly manipulate the repetition-rate difference of the dual-comb. Meanwhile, the chirp from a pump laser is transferred to all spectral comb teeth through the intra-cavity cascaded four-wave mixing process at once. After optical filtering, by beating the paired comb lines of the same order at a high-speed photodetector (PD), the bandwidth, central frequency and repetition rate of the chirped microwave waveforms are obtained. This system has a compact structure without electro-optical modulators and takes into account mutual coherence.

In this work, we demonstrate a gain-managed nonlinear amplifier with a large mode area fiber numerically and experimentally. The seed source was a home-made mode-locked fiber oscillator using a Nonlinear Amplifying Loop Mirror (NALM) that delivered ultrashort pulses with a pulse width of 8.77 ps at a repetition rate of 1 MHz. The corresponding optical spectrum centered at 1029 nm with a 3dB bandwidth of 13 nm. The pulse energy was increased to 5 nJ by a core-pumped fiber pre-amplifier. After then, a narrow-band spectral filter was inserted to reduce the pulse width and injected into a 3 m long double-clad Yb-doped fiber with a core diameter of 20 μm, which was forward pumped with a 976 nm laser diode. Finally, we obtained 1.33 μJ pulses energy delivering after amplification, and 50 fs pulses output was obtained by post compression through 600 line/mm reflective grating pairs. The numerical work has been carried out as well, which has good agreement with the experimental result. This highly compact femtosecond fiber laser system with an ultrashort pulse width has potential applications in scientific research and precision manufacturing.

We have proposed and implemented a scheme for Spiral Phase Plate (SPP) with continuous surface fabrication on fiber tips. By combining Focused Ion Beam-Scanning Electron Microscope (FIB-SEM) system and bitmap (BMP) format processing method, we fabricated a SPP with the topological charge of 1 on the fiber tip, and experimentally analyzed the diffraction and interference properties of the generated vortex beam. The experimental results were in good agreement with the simulation results, which indicated the SPP fabricated by this method had good optical properties and high reliability. This work could be valuable for fiber communication and information encryption.

A new method to analyze the wavelength-swept laser spectrum is proposed with the laser energy decomposition to a series of chirp-frequency signals, which is realized by Fractional Fourier Transform (FRFT). It can be promising to obtain a spectrum-concentrated energy distribution. In the proof-of-concept experiment, we use the Delayed Self-Heterodyne (DSH) coherent detection system to get the wavelength-swept laser signal, and the narrow linewidth of a commercial wavelength-swept laser is tested with different sweep speeds from 0.93 nm/s to 1000.03 nm/s. We explore the influence of the time window width of FRFT with different sweep speeds. Specially, we further compare the spectra by FRFT and FT in different time window widths. The narrowest linewidths calculated by FRFT, and FT are 0.14 MHz and 0.84 MHz, respectively. Finally, we compared the dynamic analysis of FRFT and traditional Fourier transform. The proposed analysis method of laser dynamical parameters will promote the understanding of laser dynamics, and benefit for the optical precision measurement applications.

A novel scheme to achieve linewidth depth narrowing and control of a single frequency Distributed Bragg Reflector (DBR) fiber laser based on distributed external feedback. Herein, the feedback signal can match the laser phase in real time to avoid the phase jump, thus realizing the laser mode is greatly suppressed. Moreover, it can also effectively suppress the unavoidable spontaneous radiation of the laser active medium, thus narrowing the linewidth in depth during the oscillation process. Based on this, the master laser can be regulated in an external all-optical approach by using a fiber device with controllable physical parameters. Eventually, an ultra-narrow linewidth laser with a spectral signal-to-noise ratio of 64 dB, a side mode suppression ratio of 83 dB, an output linewidth of 115 Hz. In particular, the Lorentz linewidth of the laser can be continuously adjusted from 115 Hz to 8.2 kHz by controlling the intensity of the distributed feedback signal. The proposed controllable mechanism of laser linewidth also provides a new perspective for extreme regulation of laser parameters of other types of lasers.

This paper comprehensively considers the suppression effect of fiber parameter control on Stimulated Brillouin Scattering (SBS), and studies the influence of different phase modulation modes, different linewidths, different fiber Yb ion densities, and different fiber lengths on the SBS threshold of the whole system, The best system setting scheme for improving SBS threshold is also given.

Graphene, as a new two-dimensional nano carbon material, has a high potential application value in the military field. At present, exploratory research has been carried out on graphene materials in infrared interference, and it has shown good near-infrared interference performance. However, its far-infrared interference performance needs to be improved, and the poor dispersion caused by its easy agglomeration also needs to be solved urgently. In this paper, Reduced Graphene Oxide (RGO) was prepared by oxidation-reduction method, and then RGO/Ni/Fe/Co composite was prepared by chemical plating method. The RGO and RGO/Ni//Fe/Co samples were characterized by SEM, TEM, XPS, EDS, XRD, etc. The complex refractive index of the samples in 2~14μm infrared wavebands was measured by ellipsometry method, and the infrared absorption characteristic was calculated by DDA method. Then, the infrared interference performance was tested by the method of Fourier transform spectrometer connected with smaller smoke box, and the dispersity was also comprehensively evaluated by Carr index method. It is found that electroless nickel-iron-cobalt plating not only can ease the secondary agglomeration between the RGO layers, improve its dispersity, but also can change the electromagnetic properties of graphene surface and significantly improve its infrared absorption. As shown in results, the average mass extinction coefficient of RGO smoke for 3~5 μm infrared was increased from 2.56m² /g to 2.75m² /g, and the average mass extinction coefficient for 8~14 μm infrared was increased from 1.8m² /g to 2.16m² /g. In particular, the far-infrared extinction performance has been obviously improved. It further indicates that the surface modification of electroless nickel-iron-cobalt plating can effectively improve the infrared interference performance of RGO smoke.

Coherent Beam Combining (CBC) can scale the overall output power while maintaining high beam quality. In recent years, this technique has also been employed to generate the high-power Optical Vortex Beam (OVB). In this work, we designed a coherent phased array, and an Optical Vortex Beam Array (OVBA) was generated via the CBC technique. Numerical simulation was studied, and an experimental setup was set up. The results showed that the OVBA could be generated in the far field. Meanwhile, the phase detection results indicated that the OVBA included several phase singularities. This work can present a new idea for manipulating the high power structured optical fields.

Chip-scale narrow-linewidth lasers have rich applications in sensing, communication, spectroscopy and light detection and ranging (LiDAR). Self-injection locking is one of the most efficient techniques to reduce linewidth significantly. By locking a laser to an external cavity, some amounts of light reflect back into the laser for mode competition, leading to a significant reduction of the lasing linewidth. In this work, we demonstrated a hybrid-integrated laser with a Microring Resonator (MRR) butt-coupled to a Distributed Feedback (DFB) laser. The radius of the MMR is designed to be 442.3 μm, corresponding to a Free Spectral Range (FSR) of about 50 GHz. And the MMR has a quality factor (Q factor) of 3×10⁶ , fabricated in an ultralow loss silicon nitride (Si₃N₄) waveguide platform. In this way, the frequency noise has been reduced to 12.565 Hz²/Hz at the 10 MHz offset frequency. Finally, 40 Hz intrinsic linewidth and 91.2 kHz integral linewidth are achieved, characterized by a delayed self-heterodyne interferometer.

Bulk single-crystal potassium dihydrogen phosphate (KDP) is a nonlinear optical material mainly used in Inertial Confinement Fusion (ICF) facility. Since bulk single-crystal KDP is fragile, various defects usually appear in the surface layer, for example, laser-induced, cutting-induced, polishing-induced and dissolution-induced defects. In present work, the x-ray grazing incidence diffraction technique (GIXRD) is introduced to investigate the structure of these defects. The GIXRD method is proved to be a nondestructive and effective way for bulk single-crystal KDP defect characterization. Based on this method, it is found that the cutting-induced defect is a polycrystalline KDP layer, while the polishing-induced defect is a heterostructure layer. Meanwhile, the dissolution-induced defect, after atmosphere dissolution and accelerate dissolution, is an amorphous layer and a KDP recrystallized layer, respectively. In addition, the depth of these defect layers can be evaluated by the GIXRD methods.

In recent years, with the rapid development of science and technology, the electromagnetic radiation is becoming more and more serious, which not only affects the normal operation of precision electronic products, but also poses a potential threat to human health. Thus, the development of absorbing materials has become a hot topic and is booming in the military and civilian fields to reduce the influence of electromagnetic radiation. Compared to some single magnetic loss materials or electrical loss materials, metal-carbon materials derived from recently developed Metal Organic Frameworks (MOFs) can combine the advantages of carbon materials and magnetic materials, they have become a hot topic. In this paper, it is proposed to prepare MOFs precursors with non-magnetic metal salt solution (Cr(NO3)3•9H2O) and magnetic metal salt solution (FeCl3•6H2O) as raw materials, and the morphology of CrFe MOFs is regulated by adjusting the molar ratio of Cr/Fe. The results show that when the molar ratio of Cr/Fe is 1:1, CrFe@C nanorods structure is obtained, after pyrolysis at 500°C in Ar argon atmosphere. The maximum Reflection Loss (RL) is -54.47 dB at 16.6 GHz with a thickness of 1.94mm,and the corresponding effective absorbing bandwidth (RL⪅-10 dB) was up to 3 GHz (15-18.0GHz).The absorbing material possesses the characteristics of high porosity and large specific surface area in structure. Among them, high porosity is beneficial to optimize impedance matching and large specific surface area promotes the scattering attenuation of electromagnetic wave, which will be helpful for obtaining excellent microwave absorption performance. Thus, in the field of microwave absorbing materials, the obtained CrFe@C structure has broad application prospects.

Compton radiography is an important diagnostic tool for Inertial Confinement Fusion (ICF), which provides important parameters about integrity, symmetry and ρR areal density of the dense cold fuel surrounding the hot spot. The dual MCPs (Micro-Channel Plate) configuration detector as a key component for Compton radiography has the ability to detect hard x-rays at energies from 40 to 200 keV with higher Detective Quantum Efficiency (DQE). In this work, a set of simulation methods for calculating the DQE and spatial resolution of dual MCPs are proposed. The photoelectric conversion and secondary electron multiplication processes of 59 KeV X-rays in double MCPs were simulated. The first piece of MCP with 51% lead content absorb x-rays volumetrically to improve the DQE and the second piece of MCP provides a large gain to multiply the secondary electrons. The simulation results indicate that the spatial resolution of the dual MCP detector is 186 μm, and the DQE can reach 6.2%, which will ensure the dual MCP-based framing cameras can obtain imploded capsule images with higher signal-to-noise ratio and spatial resolution. The influence of MCP parameters on DQE and spatial resolution was analyzed, and the simulation method will provide an important reference for further optimization of the detector.

Lead-free halide perovskite nanomaterials have aroused enormous attention and have been employed in many optoelectronic devices depending on their outstanding optical properties, especially their intrinsic stability. Regarding ultrafast fiber lasers, their high stability and low cost are crucial aspects of their industrial and scientific application. Thus, the high stable CsCu₂I₃ micro-rods are an ideal candidate for Saturable Absorbers (SA) in fiber laser systems. Herein, a passively mode-locked erbium-doped fiber laser based on CsCu2I3-SA was demonstrated operating at the communication band. To the best of our knowledge, the fiber laser could operate stably for over 164 days. These experimental results demonstrate that the CsCu₂I₃ micro-rods are ultra-stable and a promising optical modulation material to produce an ultrafast and long-stability pulse in fiber laser application.

A 2 μm band active mode-locked fiber laser with 3 m thulium-holmium co-doped fiber as gain medium is reported. According to the cavity length, the fundamental frequency is 12.24 MHz and two MZM modulators are used to obtain pulse sequences and spectrum of different repetition frequencies. When the stable repetition frequency is 489.7 MHz, the signal-to-noise ratio is 62.32 dB and the 3 dB bandwidth is 0.09 nm. A mode-locked pulse carrier of 489.7 Mb/s was obtained by synchronous digital modulation, the signal-to-noise ratio of the measured eye image was 11.1 dB.

Metasurface has the ability to manipulate electromagnetic wave in the subwavelength range, and has great application potential in stealth, detection, nuclear magnetism, high magnetic field, solar energy and microwave energy utilization, so it has been paid great attention. The physical properties of vanadium dioxide can change from semiconductor phase to metal state under certain temperature conditions, and the change is reversible. By using vanadium dioxide to design and fabricate metamaterials, temperature controlled multifunctional metamaterials can be made. This metamaterial has a much wider range of applications. Metamaterials based on vanadium dioxide have developed rapidly in recent years. Researchers have used vanadium dioxide to switch terahertz waves from spectral to spatial characteristics, tuning and dynamic control. One promising application of metamaterials is the realization of high-quality holograms. Metamaterials designed with vanadium dioxide can be used to make temperature-dependent dynamic holography. Vanadium dioxide can also be used in the optical band to regulate the absorption and reflection of photoelectric devices. In this paper, the research status in these related fields is reviewed.

The smile effect, which happens when various light-emitting units convert vertical offsets into angular offsets following fast-axis alignment, is an unavoidable part of the packaging process for diode laser arrays and has a detrimental influence on the feedback locking of external cavity diode lasers. The external cavity spectral beam combining system without output coupler, which employs the 0th order diffracted light with low grating energy to enable feedback locking of the light-emitting unit, is particularly severely impacted by the grin effect. The external cavity spectral beam combining system without output coupler uses three different types of corrective structures to simulate and explain the grin effect in various ways. The results show that while also ensuring adequate feedback and better combined beam quality, the double - separated fast-axis collimator can significantly correct the smile effect-induced beam shift. However, some light-emitting units' output beams cannot be corrected for the S-shaped smile effect with complex position offset changes. The fast-axis telescope system can effectively offset the inadequate feedback brought on by the various types of grin effect, but it is unable to enhance the beam quality of the combined beam spot, which degrades as the degree of smile effect increases. The combination of double-separated fast-axis collimator and fast-axis telescope system can complement each other to ensure sufficient feedback for different forms of smile effect to achieve stable wavelength locking and better beam quality of the combined spot.

The traditional automatic focusing method of infrared imaging system is often based on image clarity evaluation function, which controls servo motor to move from the starting position to the longest distance and finds the position with the highest image clarity evaluation function value in this path, and then controls the servo motor to move to that location. This paper puts forward a kind of infrared imaging fast automatic focusing method based on gradient calculation, which does not need to run the whole path, it firstly control the servo motor move to the position pre-calibrated, the image clarity evaluation near the position is monotonic and crest, on the basis of the feature with coarse and fine adjustment strategy for servo motor movement near the location, with less movement times, it can quickly find the position with the largest image clarity evaluation value based on gradient, so that it can quickly complete automatic focus. The experimental results show that this method can complete the auto-focusing of infrared imaging system within 3s, and the system has good stability and real-time performance.

With the rapid development of optoelectronic weapons, smoke screen as an important means of optoelectronic confrontation is receiving more and more attention. The test and evaluation of the effect of anti-infrared smoke screen interference is the basis for the development of anti-infrared smoke. Aiming at the problem of incomplete evaluation of the infrared interference effect of smoke in the indoor smoke box experiment, this paper introduced the parameters commonly used to evaluate the attenuation and suspension performances of smoke: Transmittance (𝜏), Total Obscuring Power (𝑇𝑂𝑃), Mass Extinction Coefficient (𝛼𝑚), Mass-based Composition Figure of Merit (𝐹𝑀𝑚), suspension time, deposition velocity, movement velocity with wind. The movement of smoke particles in the smoke box experiment including sedimentation, diffusion and coagulation was analyzed. The principle and method of using infrared thermal imager to test the interference performance of anti-infrared smoke in smoke box experiment were introduced. Based on the Lambert-Beer law which finds that the change process of −ln𝜏 with time is approximately a straight line, so the intercept and slope of the fitted straight line of −ln𝜏 varies with time are proposed as parameters to evaluate the attenuation performance and suspension performance of the smoke screen. The attenuation performance and suspension performance of nine kinds of smoke screens were evaluated using this evaluation method, and the results showed that this method can be used to quantitatively evaluate the attenuation performance and suspension performance of smoke screen in smoke box experiments.

Synthetic aperture techniques and concepts are widely used in radar, far-field imaging, and other important detection areas, where the application of synthetic aperture has stringent requirements for the quality and quantity of individual apertures, so there has been a significant challenge in the application of non-interferometric laser synthetic aperture techniques - reconstructing high-resolution images. The image information needs to be acquired for a long time to constrain the phase, and the results need to be reconstructed for a long time as well. In particular, for imaging rough surfaces, the removal of scattering noise often needs to be considered. Inspired by camera array imaging and deep learning in computational imaging, we uniquely apply camera arrays to optical synthetic aperture imaging systems and introduce deep learning to achieve high-resolution, high signal-to-noise imaging results of real far-field targets in a single shot. Specifically, we design a 3 × 3 camera array to acquire nine low-resolution images in parallel, each low-resolution image corresponds to a different region on the spectrum, while using a pairwise regression network to integrate the steps of sub-map acquisition, phase retrieval, and image denoising into a unified imaging system framework, driven by the data set, the neural network can quickly find the low-resolution, low-signal-to-noise ratio input in the system framework end to the high-resolution, high-signal-to-noise output end of the system framework, rather than the usual step-by-step solution. The results show that our system is able to improve the F-number from 12 to four equivalent imaging results in 0.2s, achieving a threefold increase in resolution, which allows for continuous high-resolution imaging results compared to traditional long acquisition and reconstruction. This method has the potential to break the limitations of current optical synthetic apertures and open up new avenues for fast frame rate high resolution imaging techniques.

Baffle is the primary instrument for suppressing stray radiation outside of the field of view of optical system. Infrared optical systems detect thermal radiation from objects, which can be severely affected by the stray thermal radiation. The reflectivity of the vane of the reflective baffle is so high that it can reduce the stray radiation entering the optical system, and its own radiation is small, which meets the requirements of stray radiation suppression of thermal infrared optical systems. The Stavroudis baffle is the reflective baffle with ellipse and hyperboloid vane, which has a stable structure and great capability of suppression of stray thermal radiation. But its volume will increase sharply with the increase of the field of view of the optical system. In addition, the special shape of the baffle increases the difficulty of design and processing. This paper proposes an optimize design about conical reflective baffle, which can quickly and accurately design the baffle. The volume of optimized baffle is reduced by 25% compared with the baffle designed by the original method. In order to illustrate the performance of optimized baffle, comparing with the baffle with straight vane and unoptimized baffle, we simulate the stray radiation of Three Mirror Anastigmat (TMA) with optimized baffle. The simulation results show that the Point Source Transmittance (PST) of the optimized baffle is 1×10-7 when the off-axis angle is more than 60 degrees, which is lower than the other two baffles. Finally, we propose a high-efficiency and low-cost processing method for this baffle, and the mass of baffle is within 300g. The design and processing method of the reflective baffle proposed in this paper can complete the manufacture with high efficiency and low cost, which provides technical support for infrared optical systems.

Chromatic confocal measurement is a type of non-contact measurement technology, which can be used to detect three-dimensional profile of surfaces without axial scanning. It has the characteristics of high precision and high efficiency. Line scanning chromatic confocal measurement system can obtain the depth information in the linear field of view, which can get the three-dimensional information by one-dimensional scanning, having higher efficiency compared with the point scanning type. There are two different types of design in the chromatic confocal measurement system: single- axis design and dual-axis design. The dual-axis design has several advantages over the single-axis design such as smaller effective axial spot size and higher axial resolution, and the separation of illumination system and detection system can decrease the stray light and the energy loss. In this paper, we analyze the parameters of optical system according to the practical requirements and design the optical system for a dual axis scanning confocal measurement system. Its system optical magnification is 1 and the F number is 2.5, waveband covers 450-700nm. The system uses linear variable filter to generate the spectrum, which is helpful to get the simpler system structure, the lower cost and the larger axial measurement range, compared with the traditional method using grating or prism to split the light. The visible light emitted from the light source permeates through the filter and the lens group, then the light with different wavelengths is focused on different positions on the focal plane of the measured surface. The results show that the measurement range of the system is up to 3 mm, the length of the scanning contour is up to 12 mm, and the average axial resolution is up to 1.6μm, meeting the designated measurement requirements.

Spectral accuracy is a key technical element of field hyperspectral detection. In order to meet the spectral drift and accuracy detection requirements of the field spectrometer during the mobile and long-term measurements, the research of the field spectral calibration technology based on the portable calibration light source is carried out. The light through a halogen tungsten lamp and lenses is focused on the standard material with characteristic absorption wavelength, which has 14 characteristic absorption peaks at 400-2500nm, and the wavelength accuracy is less than 0.5nm. According to the wavelength distribution curve collected by the field spectrometer, using Gaussian and polynomial fitting, the spectral calibration and detection results can be obtained. The relative deviation with the mercury lamp spectral line is less than 1nm, which verifies the applicability and accuracy of the method. The research can be used for the fast spectral calibration from 400nm to 2500nm during the field hyperspectral measurements, which can improve hyperspectral detection accuracy and efficiency.

Controlling the morphology and phase structure of low dimensional halide perovskite under photon injection is a challenging task. By using in-situ laser TEM technique, we recorded the changing process of CsPbBr3 nanocubes under laser irradiation. We found that by changing the laser fluence and irradiation time, low dimensional halide perovskite will undergo different evolution process, such as nanoparticle size variation, morphology rounding and crystal rotation. We have established a convenient laser engineering way for precise control of low-dimensional halide perovskite nanocrystals.

In order to meet the temperature performance requirements of high-precision FOG, the Shupe coefficient of the optical fiber coil must be further reduced. The generation of Shupe error is not only related to the rate of change of temperature with time, but also related to the rate of change of thermal stress with time. In this paper, the effects of thermal conductivity and internal stress of the potting adhesive on the Shupe error of the optical fiber coil were carried out. By designing a hyperbranched molecular structure, the curing stress of the UV potting adhesive was greatly reduced, and a rigid-flexible block structure was prepared by adjusting the formulation components to obtain high modulus (Eˊ) and high glass transition temperature (Tg) performance, which greatly improved the full temperature stability and long-term reliability of the potting adhesive. The potting adhesive is doped with high thermal conductivity particles to obtain high thermal conductivity, reduce the temperature gradient inside the optical fiber coil, and improve the full temperature performance of the coil. The results showed that the glass transition temperature of the developed high-precision optical fiber coil UV potting adhesive is higher than 100℃, and the Young's modulus is higher than 2000MPa. The peak-to-peak value of the coil Shupe is 0.1°/h. Through research, low stress, high thermal conductivity potting adhesive can effectively reduce the Shupe error of the high-precision optical fiber coil, improve the full-temperature performance of the coil, and realize the long-term stability and reliability of the FOG.

In order to solve the serious problem of ordinary biological microscopic objective lenses including field distortion, chromatic aberration and low resolving power, a high-resolution infinite conjugate microscopic objective with three fourth-order Zernike polynomial surfaces has been presented in this paper. The numerical aperture of microscopic system is 1.1 with 2.6mm focal length, which can be equipped with most field lens. The design and analysis results show that the par focal distance of the objective lens is 45mm, and the incidence angle and refraction angle of the optical surface of the lens are less than 60°, which meets the international standard of the microscopic objective lens. The optical Modulate Transfer Function (MTF) curve is close to the theoretical diffraction limit and the RMS wavefront error of the high-performance microscopic objective satisfied Marechal criterion. In addition, the tolerance analysis results show that the system can be processed based on the existing machining methods, despite the wavefront aberration RMS will deteriorate to 0.25λ. The whole system can be used in genetic testing research and mirror test, which is expected to promote the development of medical testing and industrial test and become one of new generation of diagnostic tools.

Since the discovery of topology, many works have been focused on periodic lattice systems, where both short-and long-range order are taken into consideration. Here, we construct a two-dimensional amorphous photonic crystal possessing short-range order, but its level of long-range order can be controlled, and experimentally investigate the transport of topological edge states in this amorphous system. We demonstrate that topology properties still remain with unidirectional edge states propagation, immune to specific disorder strength. This proposed amorphous configuration provides new opportunities to explore the relationship of the short-range order only and topology and may alleviate the fabrication difficulties to topological optical devices for practical applications.

One of the key fundamental scientific issues in the study of hyperspectral detection of oil and gas seepage is to determine the diagnostic spectral characteristics of surface soils and altered minerals during oil and gas seepage. In this study, various crude oil fractions were used to contaminate different minerals. The same crude oil was fractionated according to four temperature ranges: 0-120°C, 120-200°C, 200-275°C and 275-350°C. Subsequently, fractions from these four temperature ranges were used to contaminate four mineral powders (limonite, illite, calcite and fluorite) at doses of 1 ml to 10 ml. The spectral measurements and processing of the mixed matrices were carried out, the spectral characteristics and variation patterns were analyzed, and the spectral libraries of the four mineral mixed matrices were constructed for different crude oil fractions and different contaminated dose. The results show that all contaminated minerals have distinct hydrocarbon characteristic absorption peaks near the 1730 nm and 2300 nm positions. However, the hydrocarbon diagnostic feature peaks of the mixed matrix contaminated with crude oil are influenced by the original spectral characteristics of the minerals: the simpler the spectral characteristics of the mineral itself, the more positions of hydrocarbon absorption peak the mixed matrix spectrum exhibits, and the more obvious and prominent the characteristics. Meanwhile, the characteristic absorption peak of hydrocarbon is controlled by the type of crude oil fraction and the contamination dose. The heavier the crude oil fraction, the higher the contamination dose, the greater the absorption depth and area of the hydrocarbon diagnostic absorption peak.

Three-dimensional holographic display can provide more possibilities for the human-machine interaction in the future smart cockpit. In this paper, potential application scenarios and interaction principles of holographic display in the future automotive cockpits are predicted. VACP model is utilized to validate the interaction principles, based on the analysis and evaluation of existing and potential cutting-edge holographic display technologies. Two application patterns are set up: before 2040, the role of driver still exists due to the development of automated driving technology, participants will include only passengers after 2040, which means different interaction models and logics. After 2040, direct air projection technology will be applied, which is medium-free and with better interactive performance. Based on proposed principles, models as well as a series of user survey, application scenarios in the future cockpit are assumed. Through systematic technical analysis by cooperating with a prominent automobile OEM and other related industrial cooperators, this paper provides the principles and application concepts of holographic display in the future cockpit and obtains the evaluation and test methods for holographic display technologies in these concepts at the same time.

We have designed a fiber coupling method based on the spatial beam combining of the Photonic Crystal (PC) Laser Diode (LD). The PC LD with a small fast-axis divergence angle makes it possible to reduce the requirements for the numerical aperture and the processing precision of the optical elements, increase the alignment tolerance of components, reduce the difficulty of shaping, and improve the product yield. In the module, there is no need for the collimation of the fast-axis and slow-axis beams, which can be simultaneously focused into the optical fiber through an aspheric cylindrical lens. The simulated results, obtained by the ray tracing method, have shown a coupling efficiency of around 91.4% when the PC LD is coupled into a fiber with a core diameter of 105 μm and the numerical aperture of 0.22. Then, we have performed the experiments, and the coupling efficiency of 71.5% has been achieved. By analyzing the deviation of the simulated and experimental coupling efficiency, we have proposed several solutions. Finally, according to the strategy of this beam shaping, we also list several promising arrangements, which further prove that the beam shaping method possesses broad application prospects.

Grating Random Fiber Laser (RFL) provides feedback by writing some randomly distributed Fiber Bragg Gratings (FBGs) on the single mode fiber. However, because there are many grating pairs that satisfy the feedback condition, the mode competition is fierce, and the center frequency drift and multi-spike problems caused by gain competition are more serious. To alleviate the modes competition to a certain extent, we can reduce the spacing of FBGs and decrease the length of random structure. In this experiment, we write a random weak grating array with a spacing of the order of micrometer by using the micro-nano processing technique of the femtosecond laser, and the array length is as short as 2.5 cm. At the same time, the reflectivity of the FBG is improved by increasing the energy of the femtosecond laser pulse. The random structure length is reduced while ensuring sufficient feedback efficiency, and the mode competition and multi-spike resonance are suppressed. At the same time, we use a FBG acts as a filter, the linewidth of the RFL measured by delayed heterodyne is 377 Hz. The frequency noise of the RFL is 8 Hz/Hz^1/2 at 10 kHz, and the flatness is good when the frequency is larger than 10 kHz, which creates favorable conditions for improving the resolution of the fiber sensor.

Space-based self-organizing network is a complex network with large space-time scale, which has the gained much attention in the last decade particularly due to its characteristics of large number of nodes, complex composition, and high dynamic change of inter-satellite topology. Considering the fact that satellite node failures and link failures often occur due to network’s complexity and instability, an appropriate routing strategy needs to ensure the continuity of signal transmission and avoid the influence of link switching. In this paper, we propose a distributed destruction-resistant on-demand routing algorithm for space-based self-organizing network to give timely and accurate response to network failures. The optimal path to the destination node can be re-detected in the method of breakpoint continuous transmission. The simulation results show that the algorithm can obtain better data transmission rate and lower delay at the cost of a small amount of control overhead, ensuring the reliability and invulnerability of routing.

Three kinds of Polarization Maintaining Yb-Doped Fibers (PMYDFs) were manufactured by a Modified Chemical Vapor Deposition (MCVD) process combined with Solution Doping Technique (SDT). The laser performance of the PMYDFs were investigated by systematic experiments and a highest output power of 1812 W was achieved, corresponding to a slope efficiency of 79%. The PMYDF-3’s beam quality factor of M2x and M2y are 1.22 and 1.22 respectively at 1615 W. Through comparative experiments, the lower NA PMYDF performed a better TMI threshold.

We demonstrate a method of Photonic Crystal Fiber (PCF) inverse design for nonlinear wavelength conversion based on Four-Wave Mixing (FWM), where Deep learning Neural Networks (DNN) is applied to predict PCF structure parameters. By applying empirical formula of PCF dispersion instead of numerical simulation, a large dataset of phase-matching curves is generated of various PCF designs. The average running time of DNN prediction is 0.2s. With the help of DNN, we design and fabricate a PCF for wavelength conversion via FWM from 1064 nm to 770 nm. Pumped by a microchip laser at 1064 nm, signal wavelength is detected by optical spectrum analyzer at 770.2nm

High precision infrared lens is of great demand nowadays, especially in the area of remote sensing. The traditional optical machining method couldn’t satisfy the processing requirements neither in efficiency nor in quality. Therefore, a novel processing method was used in this paper in order to realize the concave aspherical surface in germanium (Ge) infrared lens with high accuracy. Single point diamond turning technique was first applied for the rapid promotion of surface figure accuracy of the rough machined lens. According to the measurement data obtained by non-contact profile scanning, the shape error in low and middle frequency was figured with compensation processing technology. The value of Root Mean Square (RMS) was constrained within 1/20λ at this stage. As for the residual shape error of high frequency, ion beam deterministic figuring, instead of manual operation, was employed for its high predictability and accuracy. The final RMS of this concave aspherical surface in diameter of 69 mm was improved to 1/30λ based on the above method. Meanwhile, the deviation of vertex radius of curvature was precisely controlled within 0.5 μm, which was far beyond the design requirements by an order of magnitude. The results in this paper have demonstrated that single point diamond turning of infrared lens assisted with ion beam figuring was of unique superiority both in accuracy and efficiency, which has great potential in manufacturing of astronautic optical components.

In the actual application of imaging lidar, intensity imaging is difficult to achieve due to the complex environment and weak echo signals. At this time, we can use the vibration difference between the target and the background to image the target and obtain the contour and vibration characteristics of the target. Therefore, as an important means of vibration measurement, the photon-heterodyning imaging system has important value in obtaining the speed of the target. However, due to the impact of shot noise in heterodyne detection, the speed measurement precision of the photon-heterodyning imaging system will decrease. This paper proposes a post-processing algorithm by setting an optimal photon-counting threshold between adjacent pixels to improve the resolution of speed imaging. It can well distinguish between signal and shot noise and suppress shot noise well. The simulation results show that when the intensities of signal light and the local oscillator light are respectively N_S=3 ns^-1, N_L=25 ns^-1 and the selected optimal photon-counting threshold is six, the speed measurement error is reduced from 6.43 m/s to 0.27 m/s, and the speed measurement precision is increased by 95.8%.

We experimentally showed that the π/2-period oscillation of femtosecond laser ablation threshold with laser polarization orientation can be observed in calcium fluoride (CaF₂). While the lowest single pulse ablation threshold, 5.3 J/cm², was observed when laser polarization is along the 010-crystal axis, the highest one, 5.8±0.1 J/cm², was found when angle between polarization and the 010-crystal axis were π/4 or 3π/4. The π/2-period oscillation of ablation threshold tends to be eliminated (yet still detectable) at high pulse fluence. The anisotropic ablation is possibly resulted from the different rate of avalanche ionization in different crystal axes.

Stimulated Raman Scattering (SRS) is an important nonlinear process in optical fibers that can realize the MIR wavelength shift from our existing pump source. In this paper, we experimentally investigated an efficient 2.19- and 2.42 μm cascaded Raman pulse fiber laser that was composed of 2 μm electronically modulated pulse source, one typically three-stage Tm-doped fiber amplifier and a segment of commercially nonlinear fiber. A simple single-pass configuration was built to avoid the bandwidth limitation of optical components for Raman pulse generation at longer wavelengths.

1319nm lasers have important applications in optical communication, LIDAR, laser display, laser medical, etc. In applications such as LIDAR, reliable operation over a wide temperature range is a key indicator of the laser. Vertical cavity surface emitting lasers are new pump sources for all-solid-state lasers because of their narrow linewidth, small temperature drift coefficient, and two-dimensional expansion. In this paper, we report an 808nm VCSEL end-pumped Nd:YAG 1319nm Q-switched laser that can operate stably over a wide temperature range, The whole laser is dissipated by natural conduction cooling, the VCSEL array is collimated by a two-dimensional micro lens array for beam shaping, and Nd:YAG is used as the dielectric crystal to obtain a 1319nm laser output with a maximum single pulse energy of 2.8mJ and a beam quality of M²⪅1.5 by passive Q-switching.

A novel Bidirectional output Oscillating-Amplifying Integrated Fiber Laser (B-OAIFL) which combines the advantages of the bidirectional output fiber laser oscillator, and the Oscillating-Amplifying Integrated Fiber Laser (OAIFL) is proposed and studied theoretically. The influences of the reflectivity of Fiber Bragg Grating (FBG), the length ratio, the absorption coefficient and other related parameters on the characteristics of the output laser were studied theoretically. The reflectivity of FBGs and the length of active fiber in the oscillating section show a negative correlation with the output power and efficiency. The 915 nm-pumping and the center wavelength of FBGs in the range from 1070 nm to 1080 nm show a better performance on the suppression of ASE. And the center wavelength of FBGs shows little effect on the output power and efficiency.

The theoretical model of atmospheric refractive index based on the standard atmospheric environment cannot explain the atmospheric refractive index when optical satellites detect targets. Aiming at this problem, a method for estimating the refractive index of the atmosphere based on multispectral stellar observation data is proposed. Based on optical satellites’ multispectral stellar observation data, according to the principle of deflection when the stellar light passes through the atmosphere, the optical path model of the stellar light refracted by the atmosphere is established under the assumption of a layered spherical atmosphere. A method of using multispectral segment stars to measure the actual light and the iterative forward feedback of stellar theoretical light is proposed, to estimate the refractive index of each layer of the atmosphere of the layered atmosphere to different spectral segments of light.

Optical signal receiver is a crucial element in Free Space Optical Communication (FSOC) system. Single-Mode Fiber (SMF) is commonly utilized in receivers for connecting with the subsequent optical fiber communication devices. However, the conventional SMF’s tiny core size and the random drift of the signal laser’s optical axis cause small field of view, and the optical signal acquisition and coupling issues was limited. Herein, a wide field of view optical signal receiver via pump and signal combiner was proposed and demonstrated. The experimental results show that the detection field of view of the pump and signal combiner with a 20/400 μm double-clad fiber increased about 40 times, compared with using a 6/125 μm SMF. Additionally, with the home-build adaptive fiber tip controller, the wide detection field of view can further improve the stability of optical signal receiving in the dynamic optical signal receiving system.

Target detection of arbitrary shape is widely used in remote sensing image processing, the case segmentation method based on contour regression is very similar to the target detection method. At present, many scholars have studied case segmentation using deep learning framework, case segmentation based on contour regression can be regarded as a simple extension of object detection, it is a more accurate target detection. In this paper, the contour regression method based on Fourier operator is used for accurate target detection, the Fourier feature vectors in a group of frequencies are predicted at each position of the feature map, and then the target contour point sequence is reconstructed in the image space domain through inverse Fourier transform, The simulation results show that the detection accuracy of the proposed method is more than 10% higher than that of the classical method.

Pulsed laser ranging has advantages on the long distance and short ranging time. However, in contrast with other ranging method, the ranging accuracy is relatively low. With the continuous development of imaging LIDAR products, the higher ranging accuracy is required. In order to meet the requirements of high precision pulsed laser ranging, this paper utilizes mathematical simulation software to modeling of waveform generated by different ranging environments, then takes the corresponding method to measure the distance, finally analyses and sums up for the experimental results.

Selected Laser Melting (SLM) has the advantage of high flexibility and can realize near net shape of high-precision complex components, which provides a new technological way to design and manufacture metal parts. To apply the advantages of SLM more widely in the design and forming of aerospace components, taking one connecting part of the recovery subsystem as an example, it realizes the structural optimization design based on SLM, carries out the mechanical simulation analysis, and completes the forming and processing. The results show that on the premise of meeting the application requirements, the weight of the optimized parts can be reduced by 24.54% and the overall manufacturing cycle can be saved by 41.46%, which provides an effective reference example for the process optimization design of the similar aerospace structural parts formed by selected laser melting technology.

In this work, we propose a theory of ultrafast dual wavelength pulsed laser modulation. The modulation effect of modulated light on signal light is studied based on a four-level cross absorption modulation system with the principle of in band relaxation and inter band Pauli incompatibility in single-layer graphene. The study find that the signal saturation absorption decreases with the increase of modulation intensity; in addition, modulation light and signal light also affect each other's transmittance. The model of dual wavelength synchronous laser based on modulation theory can obtain stable output. Under the guidance of this model, we have built passively Q-switched synchronous erbium-doped, and ytterbium doped fiber lasers. With the increase of pump power, the repetition rate of synchronous pulses changes from 24.50 kHz to 39.90 kHz. The laser has potential applications in Raman scattering spectroscopy, multicolor pump detection spectroscopy and nonlinear frequency conversion.

Based on the brightness value distribution of a range of shaped Gaussian laser beams measured by a CCD camera, an analytical model presenting the laser power density field has been established by using Gaussian distribution function considering the divergence characteristics of laser beams. A simulation of a sheet metal laser scanning process has been conducted by embedding the analytical model into FE software ABAQUS and compared with a corresponding experiment. The results reveal that the simulated temperature field agrees well with the measured one by an error within 7%, indicating the good accuracy of the analytical model and enhanced the foundation of the application of thermal laser scanning.

With the gradual improvement of the autonomous capabilities of Unmanned Aerial Vehicles (UAVs), the field of tasks has expanded, and it is necessary for UAVs to fully perceive target information from multiple levels and dimensions in the process of target detection and identification in the complex environment. Therefore, for UAVs, the main goal of fusion perception technology is to achieve resource interoperability and information complementarity between sensors, such as to increase the detection advantages of different image sensors in frequency, space, and time. In this paper, based on low-cost UAVs, the research is carried out from two aspects: UAVs and fusion perception sensors, and image-based fusion perception technology. The factors that need to be considered in UAVs’ sensor configuration are analyzed from four aspects: UAVs’ platform attributes, sensor attributes, flight environment, and task types and requirements. Then, we summarize the current image fusion perception technology in the process of UAVs’ detection and identification, which provides an effective reference for product development and technology research in related fields. Finally, the challenges faced by the future development of fusion technology are proposed. The overview shows that, sensor configuration scheme and information fusion scheme have the relationship of mutual promotion and restriction in the process of searching for the optimal fusion strategy. It is necessary to develop heterogeneous information fusion algorithm based on sensor characteristics. Moreover, the level of precise sensing elements, efficient information acquisition algorithms, configuration schemes and fusion algorithm implementations are required to improve for the result of 1+1<2.

Mega-electron-Volt Ultrafast Electron Microscope (MeV UEM) has become a promising tool to real-time observe ultrafast dynamics at the atomic scale, where a magnetic objective lens system is critical to manipulating the high-energy beam to achieve point-to-point imaging. However, the upper limit of spatial resolution is mainly determined by the high-order chromatic aberration resulting from the electron energy spread and the imaging lens system. A magnetic lens system based on the Russian Quadruplet (RQ) is being studied to improve the degree of symmetry and further reduce the aberration. The beam optics design and multi-target optimization are finished to achieve a good spatial resolution of point-to-point imaging. This paper will introduce the theoretical deviation and design results of our first-stage imaging lens system, and second-order beam optics is optimized further to improve the resolution.

Based on the theory of polarization conversion, this paper designs and implements two electromagnetic units with 180-degree reflection phase differences in the range of ten to 40 GHz. By coding and optimizing the spatial arrangement of the two basic units to obtain a meta surface, which makes the incident electromagnetic waves reflect diffusely and the energy in a single beam direction is reduced to realize the reduction of the Radar Cross Section (RCS). The full wave simulated show that compared with a metallic surface of the same size, the RCS of the proposed meta surface can be reduced by more than 10dB in the two broadband bands of 12.5 to 17.4GHz and 20.5 to 36.2GHz, and the maximum reduction can reach 26 dB.

In order to ensure the normal operation of the femtosecond optical frequency comb in spacecraft cabin, the thermal design was presented. The environment of the femtosecond optical frequency comb was analyzed, and its requirements of thermal control was stated. The thermal control pattern of the femtosecond optical frequency comb was depicted. This paper built the finite element model and simulated the femtosecond optical frequency comb’s two extreme conditions with the NX-TMG software. In the extreme conditions, the results of the simulation indicate that the temperature level of the oscillators and the frequency multiplier components are 27.3℃~32.9℃, and the temperature level of electronic components satisfy derating design, which could satisfy the requirements. The results of the simulation indicate that the thermal design is feasible and reasonable. Finally, the ground test is carried out. The data between test and analysis is less than 5℃, almost the same. The research jobs could give some guidance and reference for other femtosecond optical frequency comb.

Aiming at the "front door" protection problem of radar system, a waveguide plasma limiter with short response time, short recovery time and high isolation is presented based on the reflection and absorption characteristics of electromagnetic wave for High-Power Microwave (HPM) environment. A self-consistent three-dimensional (3-D) multi-physics electromagnetic-plasma fluid model coupling full-wave Maxwell’s equations with plasma fluid equations is established and solved by the Spectral-Element Time-Domain (SETD) method to describe the operating mechanism of the waveguide plasma limiter. The Galerkin’s method is employed for the space discretization and the central difference scheme is used for the temporal discretization during the SETD process. Numerical results demonstrate that the gas with low critical breakdown field strength is more suitable for protecting high-power microwaves. Our research can provide theoretical guidance for designers and give the complete physical process of plasma limiter.

Due to its high sensitivity and fast measurement, the phase-sensitive optical time-domain reflectometer (φ-OTDR) is a good candidate for distributed dynamic strain sensing and has been widely used in intrusion monitoring, geophysical exploration, and other fields. In the case of frequency scan-based φ-OTDR, the phase change is expressed as a shift in the intensity distribution. The correlation between the reference and measured spectra is used for relative strain demodulation, which imposes a limitation on the absolute strain demodulation for continuous measurements. The Brillouin optical time domain analysis (BOTDA) fortunately enables the demodulation of the absolute strain in just one measurement. A combination of φ-OTDR and BOTDA is proposed and demonstrated in this work by using the same set of frequency-scanned optical pulses, and also introducing a frequency-agile technique for fast measurements. Measurements of 9.9 Hz vibrations were made at two different absolute strains (296.7 με and 554.8 με) with a strain range of 500 nε, made possible by integrating Rayleigh and Brillouin information. The submicron strain vibrations were demonstrated by φ-OTDR signals with a high sensitivity of 6.8 nε, while the absolute strains were measured by BOTDA signals with an accuracy of 5.4 με. Thus, the proposed sensor allows dynamic absolute strain measurements with high sensitivity, thus opening the door to new possibilities yet to be explored.

In order to enhance the irradiation resistance of erbium-ytterbium co-doped optical fibers for long-range space communication applications, a Radiation-Resistant Erbium-Ytterbium co-doped Fiber (RREYDF) was fabricated by Modified Chemical Vapor Deposition (MCVD). The RREYDFs were irradiated at 300 Gy and 1000 Gy with an average dose rate of 0.2 Gy/s at room temperature using a Co60 irradiation source. The Radiation-Induced Absorption (RIA) at 940 nm and 1550 nm were 0.10 dB/m and 0.22 dB/m at 300 Gy and 0.47 dB/m and 0.36 dB/m at 1000 Gy, respectively. An Erbium-Ytterbium co-doped Fiber Amplifier (EYDFA) with a 1550 nm signal and a 940 nm pump source was built for gain testing. The Radiation-Induced Gain Variation (RIGV) was 0.1 dB (300 Gy) and 1.0 dB (1000 Gy) at a pump power of 7.3 W.

This paper summarizes the existing technologies in the field of photoelectric countermeasure, discusses the challenges faced by laser angle deception jamming technology, and comprehensively expounds the development direction of photoelectric countermeasure in the field of laser angle deception jamming. In the field of laser jamming technology, the different ways of laser jamming technology and the development of laser jamming weapons are studied. Through the analysis of the principle of laser semi-active guidance and laser angle deception jamming technology, it is found that the traditional laser guidance technology can be intercepted, copied and finally released by our side for decoying because of the simplicity of its laser coding, but facing the new laser guidance technology and the improved laser coding technology, our laser decoying system will face the risk of failure. Therefore, the future laser angle deception jamming must solve the problem of how to avoid the influence of laser coding technology on laser decoy jamming.

Hollow-Core Fiber (HCF) has attracted great interest from researchers because of its high damage threshold and small nonlinearity compared with solid-core fiber. However, how to reduce the loss of HCF has always been an urgent problem to be solved. Aiming to solve the problem, we propose a novel Hollow-Core Negative Curvature Fiber (HC-NCF) with an elliptical nested tube and a circular nested tube. The structure of this HC-NCF is relatively simple, which greatly reduces the difficulty of fabrication. Finite element modeling has been used to simulate and calculate the Confinement Loss (CL) and Bending Loss (BL) of the fiber with different nested tube structures. Results show that the CL of the LP01 mode is as low as 6.48×10-6 dB/km at the interesting wavelength of 1.06 μm. It exhibits a minimum CL of 5.28×10-6 dB/km at 1.01 μm with maintaining a loss of less than 0.003 dB/km over 1020 nm (0.77 μm to 1.79 μm) bandwidth. In addition, we proposed the HC-NCF has been confirmed to have better-bending resistance. Within a bending radius of 5–40 cm, the HC-NCF has a BL below 3.75×10-4 dB/km at a 10 cm bending radius; the BL is below 1.03×10-5 dB/km at a 40 cm bending radius.

The combination of numerous signals for a spatial diversity Free-Space Optical Communication (FSOC) framework can be actualized based on fiber-optic devices or digital signal processing. The optical combination process is normally achieved in binary tree structure to cascade multiple signals, so the number of input laser beams is subject to binary condition. In this article, we coherently combined an arbitrary number of laser beams by using a modified scheme based on the fiber couplers with specific coupling ratios. The theoretical research of three fibers combination is expressed and the practical combining efficiency of 98.3% is obtained in the experiment, which surpasses the theoretical greatest combining efficiency of customarily using 3-dB couplers. For a particular spatial diversity antenna that consists of 19 apertures, we designed its optical combination module based on specific fiber couplers. In the condition of phase differences among 19 input beams are compensated with SPGD algorithm, the average output power rises 25 to 40 times in the closed loop; the experimental combining efficiency reaches 56.5%, which is very close to the transmission efficiency of 59.3% where the combined module serves as a laser splitter without phase compensation. It means that overlooking the devices’ insert losses, the coherent combining efficiency reaches 95.3%. This study shows that optical combination provides an effective alternative for the digital signals combining process in spatial diversity FSOC.

In view that the sun is a main stray light source for space-based camera with wide filed as high-intensity light, the influence on the image quality of the camera was studied. Through the design of the camera’s lens hood, the number of stray lights scattering on the surface of the lens is reduced. Then the stray light which can reach the detector is diminished. Compare the image quality of the flying surveillance camera with which before the lens hood designed, the maximum value of PST(θ) outside the critical angle 55° was reduced to 1.1099×10^-9. Stray light was significantly inhibited, and the image quality was effectively improved.

Polarization beam splitter is an important part of many optical systems. The polarization beam splitter based on meta surface has the advantages of high efficiency, large splitting angle, wide bandwidth and easy fabrication. Here, we propose a double-layer Metal-Dielectric-Metal (MDM) structure. Through the periodic arrangement of metal nano bricks, the length and width in the nano brick are used to realize the independent control of the reflection phase of the orthogonally polarized light. The top and lower antennae are in charge of the anomalous reflection in the VIS and NIR spectral band, respectively, which render an ultra-broadband polarization beam splitting meta surface with a spectral bandwidth of 500-1400 nm, exhibiting an average anomalous reflection efficiency over 60 %. We hope that our design can provide a new solution for the realization of ultra-broadband beam splitter based on meta surface.

To realize the highly sensitive detection of trace H₂S in SF₆, a multi-Mechanism Enhanced Photoacoustic Spectroscopy Analyzer (MEPSA) is proposed. A resonant Photoacoustic Cell (PAC) is used to enhance the photoacoustic signals. An ultrasensitive optical fiber acoustic sensor based on a silicon cantilever beam is used for mechanical resonance enhancement of photoacoustic signals. An Erbium-Doped Fiber Application amplifier (EDFA) was used to cascade a DFB to increase the excitation light power. The noise equivalent minimum detection limit of H₂S under the SF₆ background is 0.15 ppm.

The design and production of metallic mesh based on germanium substrate were investigated to satisfy the electromagnetic shielding requirements of germanium optical windows. Through theoretical analysis of the effect of metallic mesh structure on optical transmittance and electromagnetic shielding effectiveness, CST software is used to simulate the effect of metallic mesh period, thickness and substrate resistivity on electromagnetic shielding. According to the simulation results, appropriate parameters are selected to prepare the mesh microstructure. The mesh structure that meets the requirements was produced using laser direct writing lithography. The metallic mesh microstructure has a 400 μm period and a 12μm line width. The eight to 12μm bands measured by the infrared spectrometer had an 87.1% transmissivity. The lowest electromagnetic shielding efficacy is greater than 28.1dB, while the average electromagnetic shielding efficiency of the 240MHz to 18GHz range is assessed by the vector network analyzer at 34.4 dB. This paper describes the simulation and fabrication of metallic mesh microstructures on germanium substrates. These microstructures have excellent optical and electrical properties, which is very important for the creation of optical windows with high optical transmittance and potent electromagnetic shielding.

Single Bubble Sonoluminescence (SBSL) represents a light-emitting effect from a bubble driven by ultrasound. In this work, SBSL phenomenon in potassium dihydrogen phosphate (KDP) solutions was studied. SBSL intensity in KDP solutions with respect to ultrasonic amplitude and frequency, concentration and temperature was measured and analyzed. Result shows that stable SBSL can be realized around 27.6 kHz. Meanwhile, it is found that the optimal driving frequencies and driving ultrasonic amplitudes of SBSL are substantially affected by the liquid temperature and concentration. SBSL in water was used as a reference, and comparison between results for KDP solutions and water shows different trends. In the measured spectra of SBSL in KDP solutions, the characteristic emission lines of ions were not found, which indicates that the ions in the solution did not or hardly participate in the sonoluminescence process.

Phase retrieval is one of the vital processes in many computational imaging techniques, aiming at retrieving the lost phase of light fields from the corresponding intensity. Recently, advanced deep learning strategies for phase retrieval have gained much attention mainly due to their highly efficiency and accuracy compared with conventional iterative methods represented by Gerchberg-Saxton algorithm. Here, we propose a self-supervised neural network integrated with angular spectrum transform to retrieve lost phases of color images. The network contains two complex-valued U-Nets to restore and update the light fields of the image plane and the object plane, respectively. By minimizing the difference between the reconstructed images from the network with the input images, complex light fields on the object plane can be obtained. The proposed network is able to retrieve missing phases of 200 color images within half a minute while the averaged peak signal-to-noise ratio and structural similarity of the reconstructed color images can reach 23.21 dB and 0.84, respectively. Visualization and statistic results indicate that our network is an efficient and accurate method of phase retrieval, which has potential applications in many fields of computational imaging.

A narrowband fast tunable acousto-optic filter is proposed and demonstrated based on the acoustically-induced birefringence of dispersion compensating fiber. The band-pass and band-stop filtering characteristics of the filter are realized through the mode coupling caused by the acoustic vibration generated by the device. At the same time, the single wavelength filtering effect with the bandwidth of about 7nm is realized by optimizing the operating distance of Acousto-Optic Interaction (AOI) length. The constructed filter obtains the advantages of narrow band, fast tuning speed, single wavelength, compact size, simple fabrication and zero frequency shift. It has potential applications in the fields of tunable lasers, wavelength division multiplexing optical communication and optical signal processing.

In this paper, we proposed a multilayer Metamaterial Absorber (MA) to enhance the up-conversion emission, which consists of silver grating, Up Conversion Nanoparticles (UCNPs) and silver film. Numerical and theoretical analysis results showed that tremendous up conversion enhancement is achieved at three wavelengths due to the surface plasmon resonance. Moreover, it was found that the interaction between the silver grating and the silver film is critical to the up-conversion enhancement. Tuning the thickness of the silver grating, the maximum enhanced factor (EFups) of 980 nm is 4 6.5 10⁴. This metamaterial absorber provided a novel approach in enhancing up conversion, and the research findings could be helpful to the design of biosensor and photovoltaic devices.

Traditional analytical algorithm needs to combine the transmission functions of grating and lens to generate a Computer Generated Hologram (CGH), so as to realize the distribution of three-dimensional (3D) multi-focal points in space, but the grating phase will inevitably produce high-order diffraction focus, resulting in energy loss, and the traditional analytic algorithm is more suitable for generating array multi-focal distribution with equal spacing. To solve this problem, this paper simplifies the traditional analytical algorithm, and proposes a method that only uses multi-lens phase and random phase superposition to generate the CGH required by the target light location, by changing the focal length of the lens phase, the multi-focus distribution along the z-axial direction of multiple independent focal planes is realized. Then the phase of these different focal planes is superimposed, and a 0~2π random phase modulation is added, which can quickly generate 3D multi-focus distribution with controllable number and position. The simulation results show that the energy uniformity of focal spot on each focal plane is between 89.45% and 98.08%. The experimental results show that the energy uniformity of focal spots on each focal plane is between 88.40% and 96.13%, which is consistent with the simulation results. Compared with traditional analytical algorithm, the proposed method is more universal for multi-focus distribution in 3D space without special requirements of array distribution with equal spacing, and has potential application value in laser processing, holographic optical tweezers, optical communication and other fields.

Bismuth (Bi)-doped silica-based glasses and fibers are attractive materials for the new optical amplifiers and tunable lasers. In this paper, Bi/Al co-doped silica glass with a relatively high Bi concentration (0.552 wt.%) were prepared by using the optimized sol-gel method. Hydrofluoric acid (HF) was used as a catalyst in the reaction, which reduced the hydroxyl to lower than 5ppm in the final glass. After the process of drying and sintering, the gel was turned into the transparent glass at low temperature (~1300 °C). The optical properties of Bi/Al co-doped silica glass were also investigated. Excited by a 980 nm laser diode, broadband fluorescence centered at 1114 nm was obtained, which was ascribed to the Bi-Al active center (BAC-Al). The emission cross-section (𝜎𝑒𝑚) was calculated to be 7.4 × 10⁻²¹ cm² for BAC-Al. In addition, ultra-broadband emission ranging from 850 nm to 1700 nm was also obtained excited by the 808 nm LD, which might be ascribed to BAC-P overlapped by other BACs. After the gaussian separation of fluorescence peak, the emission cross-section for BAC-P was 13.4×10⁻²¹ cm². Our results confirmed the potentialities of the optimized sol-gel method in Bi-doped glass fabrication. The Bi/Al co-doped silica glass prepared in this work were promising to develop Bi-doped fibers and relative devices.

The complex refractive index is an important optical constant, which is usually used to describe some optical properties of absorptive media. The extinction efficiency factor is calculated by the ratio of the extinction cross section of the material particle to the maximum cross-sectional area of the particle. It is numerically equal to the sum of the scattering efficiency factor and the absorption efficiency factor and is often used to characterize the optical attenuation properties of optical attenuation materials. In the present study, the complex refractive index of optical attenuation materials is often calculated by spectral testing and Kramers-Kronig algorithm and the extinction efficiency factor of materials is obtained by calculating the single scattering parameters by discrete dipole approximation. However, the effects of complex refractive index of the optical attenuation material on its extinction efficiency factor have not been studied. It is meaningful to study the effects of complex refractive index on extinction efficiency factor, which can further study the relationship between the attenuation properties of optical attenuation materials and their material properties.

This paper proposes and verified a modified cavity configuration in oscillating-amplifying integrated fiber laser for stimulated Raman scattering suppression. A short segment of YDF and a long piece of GDF is used in the oscillating section, which can simultaneously suppress the onset of Raman component and avoid the self-pulsing operation caused by the extremely low gain in cavity. Experimental result shows a 31dB Raman suppression ratio at 1080nm when output power reaches 5kW without any other Raman suppression element.

We demonstrate an all-fiber SC laser source based on a 0.9 m-long 94 mol.% GCF which was pumped by a Single-Mode (SM) TDFA-based 1.9~2.7 μm laser source. A 2.59 W flat SC spectrum with coverage of 1.9~3.5 μm were achieved under a seed pulse repetition rate of 600 kHz and a pulse duration of 1 ns. The 3 dB bandwidth was 1210 nm ranging from 1970 to 3180 nm and the 10 dB bandwidth was 1380 nm ranging from 1920 to 3300 nm.

With a homemade (1+1) side-pumped fiber and 1018 nm tandem-pumping strategy, we report an experimental demonstration of 17.4 kW power output, which is apparently a remarkable achievement. The (1+1) side-pumped fiber consists of an active core, highly doped with Ytterbium up to 2000 ppm, and a pump core to transport intensive pumping power through a homemade 5×1 combiner. Stimulated Raman scattering suppression ratio at maximum power is improved to 37.8 dB due to an array of connected tilted fiber Bragg gratings performance. So, the experimental result clarifies the feasibility of combining side- and tandem- pumping in ultra high power scale of tens of kilowatts.

Supercontinuum (SC) sources have extensive applications in tomography, spectroscopy, and communications. Numerous applications, including ultrahigh-resolution optical coherence tomography, free-space broad-spectrum optical communication, high-speed imaging, spectroelectrochemical ellipsometry, and spectral sensitivity evaluation are based on SC. SC generation in optical fibers could be easily observed in the anomalous dispersion region near 1.5 μm. Indeed, in the normal dispersion region, the modulation instability induced by cross phase modulation could also generate the SC. In this study, an all-fiber-integrated high-power tandem-pumped random Raman laser amplifier is built for SC generation in normal dispersion region. The output power exceeds 1 kW. And the spectrum covers the range from 1.07 μm to 1.6 μm.

The interference factors produced by the strong radiation interference source in the infrared imaging system are mainly: super-saturation crosstalk effect, spatial transfer characteristic ambiguity phenomenon, halo effect and transient environmental temperature adaptability. These interference phenomena will reduce the imaging of the infrared imaging system, produce instantaneous “blinding” or key information loss, and affect the advantages of the system in target detection, capture, identification and tracking. The formation mechanism and theoretical basis of each influencing factor are analyzed, and the methods of eliminating interference characteristics are studied. Through experimental research, the method of judging the imaging quality of the infrared imaging system at different temperatures is studied. The results show that the temperature adaptability of the infrared imaging system greatly affects the performance of the system detection and recognition. Therefore, the research on the temperature adaptability of the infrared imaging system can provide a basis for the quantitative characterization and simulation calculation of the interference characteristics of strong radiation sources in order to increase the application of the system in the research field and propose ideas for further research.

The traditional laser power supply is built and become of analog circuit, and the precision requirements of circuit design and automatic control are difficult to meet the aerospace level. Therefore, it becomes particularly important to realize the all-digital design of spaceborne laser power supply. On the basis of FPGA technology, we design a kind of Ethernet protocol, 422 level transmission form to realize the communication with the management controller, and provide laser timing signal, Q-switched signal, AD/DA control signal for the laser. In this way, the transmitter timing and parameter adjustment functions such as charging current, charging high voltage, LD discharge current, LD drive timing sequence, Q-switching drive high voltage and Q-switching drive timing sequence which required by the laser can be realized. In addition, when the charging high voltage, charging current and LD discharge current exceed the threshold, the transmitter can be turned off automatically to realize the automatic protection function. The test results show that the design of all digital spaceborne laser power supply meets the functional requirements.

With the development of technology and the need for perception of complex surrounding environment information, LIDAR (light detection and ranging) systems have more application scenarios - blind navigation is one of them. However, the current LIDARs on the market generally suffer from near range blind spots of several meters. For the blind, close information perception is very important for their travel safety, and of course long-distance information perception is also necessary. Therefore, we discussed the difference between coaxial and non-coaxial LIDAR systems, and designed a LIDAR system for blind navigation based on an off-axis parabolic receiver, which is capable of a near detection range of less than 30 cm.

1090 nm all-fiberized and Polarization-maintained fiber laser with narrow linewidth and near-single-mode beam quality is demonstrated. We obtain a 668 W narrow linewidth linearly laser output with a linewidth of about 22GHz, the polarization extinction ratio is about 14dB, and the M² is less than 1.1 at the maximum output power.

Intelligent recognition camera for electric transmission line status plays an important role in electric power transmission in our country, and the ice environment will bring severe challenges to its normal use. Based on the analysis of the harm caused by the icing environment to the status intelligent recognition camera, this paper proposes that it should be very necessary to carry out icing test in laboratory to reform the weak points of products. According to the proposed verification conditions, the icing test device is designed and developed, and tested in the laboratory. Finally, it is proved that the icing test device meets the requirements of the verification conditions and can be used for the electric transmission line status intelligent identification camera to carry out icing test.

Aerodynamic lenses can increase the local particle number density of the aerosol beam. The particle number density of aerosol has an important effect on the excitation probability and spectral intensity of laser-induced plasma. Therefore, aerodynamic lenses have the potential to improve the identification efficiency of Laser Induced Breakdown Spectroscopy (LIBS) in aerosol real-time monitoring. In this study, the effects of an aerodynamic lens on laser excited aerosol particles were developed by experiments and simulations. The process of aerosol beam passing through an aerodynamic lens was simulated by using the CFD software FLUENT. The simulation results show that the setup can increase the aerosol concentration by three orders of magnitude. The Aerosol Focusing-Laser Induced Breakdown Spectroscopy (Aerosol Focusing-LIBS) experimental setup is established. The experimental and simulation results are in good agreement. And the experimental results show that the laser excitation probability has increased by about 5 times, the average intensity of the excitation spectrum has increased by about three times.

A kinematic mount based on the statically determinate principle is designed using a single-axis right circular flexure hinge. The main role of this support structure is to reduce the influence the satellite platform on the space camera, thereby ensuring the thermal stability of the space camera in orbit. The mathematical model of the compliance of the single-axis right circular flexure hinge is derived based on the Castigliano’s second theorem. According to the index requirements and the compliance equations, the initial structure of kinematic mount is obtained. The optimization design is conducted with the initial structure as the optimization object and the natural frequency as the optimization objective to obtain the optimal structure. The finite element analysis shows that the optimal structure meets the index requirements. Compared with the initial structure, the natural frequency of the optimal structure is increased by 4.2%, the optimal structure in Rx, Ty, and Tz are better than the initial structure 13.3%, 21%, and 12.8%. Experiment verifications of compliance equation C33 of single-axis right circular flexure hinge and the compliance of the bipod are carried out. The experiment results indicate that the compliance equation C33 is correct, and the compliance of the bipod meets the design value. Therefore, it is concluded that all the compliance equations are correct, and the kinematic mount can meet the requirements of the thermal stability of the space camera in orbit.

We propose a novel design of two-dimensional geometrical waveguide combiner, which integrates the vertical pupil expansion area and horizontal pupil expansion area into one planar waveguide. Different from previous solutions, the proposed design allows larger FOV and easier pupil matching with compact structure. The relationship between maximum vertical FOV and slanted angle of partially reflective mirror array, the exit pupil matching method for vertical and horizontal FOV are discussed. Then the optimization process of the waveguide structure to obtain a large FOV and uniform illuminance is showed, and the simulation shows that the method is solid. The FOV of the designed waveguide combiner is 𝑉FOV × 𝐻FOV 33° × 49.5° and diagonal FOV 57.4°, and the thickness of the waveguide is 1.7𝑚𝑚.

Two types of FBG were fabricated in the 20/400μm passive Double-Clad Fiber (DCF) without coating (w/o-coating) and with coating (w-coating) by femtosecond laser plane-by-plane technology. The w/o-coating FBG with a central wavelength of 1060.62 nm, a reflectivity greater than 99.5% and a 3dB-bandwidth of 3.52 nm, the w-coating FBG with a central wavelength of 1080.10 nm, a reflectivity greater than 99.9% and a 3dB-bandwidth of 2.87 nm, respectively. To the best of our knowledge, this is the first report of fabricating high quality fiber Bragg grating in 20/400μm DCF using femtosecond laser direct writing method.

Distributed High-Temperature Sensing (DHTS) system with Single Crystal Fiber (SCF) has been proved to be an efficient method for ultra-high temperature sensing where traditional silica fiber can’t survive. The performance enhancement of the system has been a long desire to better support various applications. In this paper, the upgraded DHTS system used 532 nm laser to avoid thermo-noise at ultra-high temperature and detected the backscattered Raman Stokes and Anti-Stokes signals in a sapphire fiber. The measurands indicated a 7 cm spatial resolution and a 2.2 ℃ temperature resolution with only 30 s average time. The system is expected to be applicable for important applications such as aircraft engine and energy monitoring with further improvements.

Grating devices are widely used in optical force or vibration sensing. However, conventional gratings made of rigid materials have small strain which only arises little change of the resonance wavelengths by force, furthermore the resonant wavelengths are susceptible to temperature and humidity, thus accurate perception of pressure is hard and complicated. In this work, we designed and fabricated a flexible and stretchable PDMS-TiO2-PDMS grating waveguide type pressure sensor where the sensing mechanism is based on waveguide resonance, meaning the resonant wavelengths are shifted linearly with the change of grating pitch and are rarely affected by temperature and humidity. Finite element analysis (COMSOL Multiphysics) is used to simulate the dynamic deformation of the grating structure under stress or tension, and the spectral changes of the gratings under above mechanical conditions are simulated by using Finite Difference Time Domain (FDTD) simulation. We found that the wavelengths of waveguide resonance are in good linearity to the changing of grating period and is insensitive to the grating height and line width. The proposed flexible grating device provides a new sensing method for optical sensors, which can be practically applied in various circumstances including strong electromagnetic interference and high variation of temperature or humidity.

In this paper, we designed a Slab Coupled Optical Waveguide (SCOW) DFB semiconductor laser around 1550 nm with increased output optical power and single mode operation. Under the assumption of idea heat dissipation, we simulate the performances of the designed DFB laser using PICs3D software. A Continuous-Wave (CW) output power of 1.03 W is obtained under the bias current of 2.7A, with the slope efficiency of 0.402 W/A. Because of the asymmetric Separated Confinement Heterostructure (SCH) and the passive waveguide structure, the mode profile is expanded. Then, single mode outputs with near-field mode spot size of 5 μm×5 μm and the Full Width at Half Maximum (FWHM) far-field divergence angle is as low as 9.2°×16.2°. Therefore, the designed 1550 nm high power DFB semiconductor laser has potential applications in the fields such as silicon-based photonics integration, Free Space Optical (FSO) communication and light detection and ranging (LiDAR) systems.

The tandem pumping technique has been proven effective in power scaling of fiber lasers, which enabled the most powerful high-brightness fiber lasers to date. However, further performance improvement of tandem-pumped fiber lasers is challenged by the contradiction between nonlinearity suppression and good beam quality maintaining. To address these challenges, researchers from worldwide devoted to expediting the development of high-power tandem-pumped fiber lasers, and a series of new results and new applications emerged in recent years. This paper will highlight the recent advances in the enabling techniques of high-brightness tandem-pumped fiber lasers and the new applications of tandem pumping since the first review paper on this topic in 2017. A brief outlook on the further development of tandem pumping technique is also given.

In view of the characteristics of low precision, unstable quality and high rejection rate of the current gas film hole molding, there is no universal and engineered gas film hole detection equipment in China. A set of image detection equipment based on machine vision is developed to improve the efficiency and accuracy of the gas film hole detection. According to the depth of field synthesis and three-dimensional reconstruction technology, the resolution of pixels of different pictures in the same location is analyzed. Thus, the evaluation function of the pixel is obtained, and then each pixel is calculated, and the depth information of the pixel is given to complete the three-dimensional reconstruction. This paper proposes a method for evaluating the pixel clarity of gas film holes in turbine blades. Since the edge detection algorithm of traditional Sobel operator is poor, this paper proposes four-direction and eight-direction Sobel operators to evaluate the pixel clarity of standard measure blocks with the same material of gas film holes by giving different weights. Then, according to the experimental results, the window size of pixel sharpness evaluation was discussed, and the clarity ratio, steepness, local extreme factor and sensitivity of different window sizes were calculated respectively. Finally, the window size suitable for the evaluation of pixels in the air film hole was obtained. Finally, all the pixels were calculated, and the calculation results were compared with the real situation to verify the correctness of the proposed algorithm.

Using a picosecond pulse laser seed source with nonlinear frequency component, the laser with nonlinear fiber amplifier is constructed to directly produce supercontinuum. The problem of reverse light in nonlinear amplification is effectively solved. In the experiment, SESAM passively mode-locked picosecond pulse is used to achieve first-stage stokes frequency extension through two-stage amplification. Finally, the third-stage nonlinear fiber amplifier is used to achieve the supercontinuum output with the wavelength coverage range of 950 to about 1650nm, flatness of 10dB and output power of 56W.

In this work, a high-power polarization-maintained fiber laser with ultra-narrow linewidth and near diffraction limited beam quality is demonstrated. The stimulated Brillouin scattering is mitigated by optimizing phase modulation scheme, the mode instability is suppressed by coiling the active fiber, and the output power reaches to 3kW at the full width at half-maximum linewidth of 10.6GHz. At maximum output power, the stimulated Raman scattering suppression ratio reaches to 75dB, the polarization extinction ratio is 96%, the beam quality M² is 1.156, and the further scaling of output power is limited by stimulated Brillouin scattering effect. To the best of our knowledge, this is the highest power for polarization-maintained fiber laser with about 10GHz linewidth ever reported so far.

We demonstrate visible random lasing with the tunable range from 560 nm to 630 nm from a dual-wavelength tunable Random Raman Fiber Laser (RRFL) with phosphosilicate fiber. By tuning the pump wavelength and the reflecting wavelengths of the point reflector consisted of two separated gratings, the wavelength of RRFL can be tuned flexibly in either single wavelength or dual wavelength emission operating mode. Based on such dual-wavelength switchable and tunable RRFL and the Periodically Poled Lithium Niobate (PPLN) crystal array with various grating periods, 560 nm-630 nm widely tunable random lasing can be generated via Second Harmonic Generation (SHG) and Sum Frequency Generation (SFG).