This PDF file contains the front matter associated with SPIE Proceedings Volume 12154, including the Title Page, Copyright information, and Table of Contents.

A novel gas pressure sensor is designed and demonstrated experimentally, which is composed of a Fabry–Perot cavity based on a quartz capillary filled with polydimethylsiloxane (PDMS). The PDMS has excellent elasticity and is an ideal material for gas pressure sensing. The experimental results show that the sensor has a high sensitivity as the gas pressure increases (or decreases). When the gas pressure rises, the maximum sensitivity reaches the -15.95 nm/MPa. When the gas pressure drops, the maximum sensitivity reaches -23.1 nm/MPa. Experimental results show that there are large differences in the sensor sensitivity when the gas pressure rises or decreases, which may be related to the characteristics of the PDMS. The designed sensors have the advantages of simple and compact structure, low cost and high sensitivity, and have certain application prospects in engineering practice.

Multiple-Input-Single-Output (MISO) is a promising application for visible light communication (VLC) system, which is featured in large user capacity, but also suffers from the nonlinearity problem introduced by the light emitting diode (LED) itself and the signal superposition at the receiver. In this article, to suppress the negative effect of nonlinearity in MISO VLC system that utilizes superposition modulation, we proposed a solution that applies Nonlinear Trellis-Coded Precoding (NL-TCP) to shape the spectrum and constellation diagram of the original PAM-4. A PAM-6 signal converted from PAM- 4 by NL-TCP algorithm successfully lowers its BER under the threshold for 7% FEC and supports up to 1.1 Gb/s data rate within severe nonlinearity, while the conventional PAM-4 modulation fails to meet the threshold requirement. The maximum improvement in Q-factor recorded is 1.2dB at the data rate of 1 Gb/s. In comparison, NL-TCP is more sensitive to the data rate, but it has a more desirable robustness against the nonlinearity in the channel. This experiment verifies the practical benefit of NL-TCP in high nonlinearity channel. It is believed that this research is significative for the researchers who are aimed at establishing a usable link, yet have to tolerate the nonlinearity to exist in the channel.

This article introduces a new type of liquid-core hydrogel optical fiber preparation method, the structure of the liquid core hydrogel optical fiber is composed of an ultra-high refractive index liquid core, a high refractive index inner cladding and a low refractive index outer cladding. Since the refractive index of the liquid core is greater than the refractive index of the cladding, light can be propagated in the liquid-core by the principle of total reflection. The light energy of the liquid-core hydrogel optical fiber is mainly distributed in the liquid-core region. Compared with the solid core and hollow core hydrogel optical fiber prepared from the same material, the hydrogel optical fiber has a lower optical loss rate. Compared with traditional quartz optical fiber, the optical fiber has simple preparation method, low manufacturing cost, and good material flexibility. Due to the high biocompatibility of the hydrogel material, the optical fiber can be applied to optical sensing in a wider range of fields; In addition, the hydrogel material has good flexibility and expandability, can be compatible with the existing optical fiber system, and has good application prospects in the fields of biochemical detection, light transmission in vivo, and so on.

Optical chaotic communication as one of the encryption communication technologies has been get a great development in recent. However, various of hacking attacks from eavesdropper are threatening security of chaotic communication system. Therefore, we propose an novel system which combined with chaotic encryption module and phase perturbation module targeting to achieve a security-enhance chaotic communication system. Simulation result demonstrate the system provide a high-security transmitting performance with on a bit rate over Gb/s and satisfactory BER is achieved.

Secure key distribution is one of the most crucial issues for the security of communication systems. However, it is extremely challenging to realize the gigabit key distribution required for high-speed secure communication. Targeting high-speed secure key distribution, we propose a novel scheme based on chaos synchronization and optical frequency comb technology. By the multi-channel multiplexing, final security key rate is greatly extended to gigabit. The feasibility and performance of the proposed high-speed secure key distribution scheme are verified by numerical simulations.

The nonlinear effect is the main factor limiting the performance of high-speed optical network. A high nonlinear tolerance 160Gbit/s Apol-FSK modulation format for 5G backhaul network is proposed.

As an important physical quantity, the temperature detection is necessary. Based on the demand for temperature detection in harsh environment, the optical fiber fluorescent temperature sensor has been developed. Most of the sensing probes were prepared by doping fluorescence substance into optical fiber or modifying them onto the optical fiber surfaces. However, the former requires expensive equipment, while the latter suffers from instability. Here, we propose a method of encapsulating the temperature-sensitive material of rhodamine B (RhB) in a capillary glass tube to prepare the sensing probe which only relies on extremely simple fabrication operation and cost-effective materials. The sensing probe is connected with the fiber-coupled laser and smartphone through a 2x1 fiber coupler, which are respectively used to excite and collect the fluorescent signal of RhB. The optimization of the capillary tube length, the tube wall thickness, and the immersion depth of light fiber show that these parameters have little influence on the performance of the sensor. By placing the sensing probe in the water bath, the temperature ranging from 30 °C to 70 °C. The sensor is proven to good sensitivity, stability and reusability.

We proposed a novel method to improve the measurement accuracy for temperature in optical fiber sensing based on Brillouin intensity compensation. A model of Brillouin intensity compensation is proposed to improve the measurement accuracy for temperature, which can effectively calculate the attenuation of Brillouin intensity along with the sensing optical fiber. After intensity compensating of Brillouin signal based on the model, we can accurately quantify the relative variation of Brillouin intensity along with the sensing fiber. The parameters of Brillouin intensity compensation are modified by combining the experimental data of the sensing fiber under different temperatures. To verify the demodulation effect of the model in optical fiber sensing, the obtained results through the above model are compared with the ones with the traditional solution method. The deviation analysis proves that the measurement accuracy can be improved by more than 8%.

Magnetic field as a kind of objective substance contains abundant physical information, so high sensitivity and resolution measurement for the magnetic field has great significance in scientific and industrial fields. In this work, we propose a novel fiber-optic magnetic field sensor by using an etched fiber Bragg grating (FBG) in conjunction with an OEO. A commercial FBG was firstly dipped into mixed hydrofluoric acid solution to remove cladding layer, and then was embedded with Fe3O4 magnetic fluid as sensing element. Incorporating the microwave photonic filter (MPF) in the OEO sensor, the oscillation frequency is determined by the magnetic field. Experimental results show that the oscillation frequency decreases with the increment of the magnetic field with sensitivity of 15.2Hz/Oe ranging from 3mT to 10mT, mainly because the refractive index of magnetic fluid was reduced sharply in this range. Since the proposed method transfers the measurement from the optical domain to electric domain, the interrogation speed, sensing sensitivity and resolution are significantly increased, offering potentials in many fields where the magnetic field measurement is required.

A carrier phase recovery algorithm using generalized circular harmonic expansion is proposed for probabilistically shaped M-QAM systems. Compared with two-stage blind phase search and Kullback-Leibler divergence based algorithms, a higher laser linewidth tolerance is achieved.

Single frequency laser sources with high frequency stabilization serve as the backbone for the fields from advanced scientific experiments to industrial or commercial applications, thanks to the rapid development of laser frequency stabilization techniques based on optical or electrical feedback from an external reference. Despite the tremendous progress, it still remains an open question as to how to realize a laser source that can reach the high frequency stabilization and still remain sufficiently compact and portable for field use, with the increasing interest in applying these systems outside of the laboratory. Here, we describe a frequency stabilization DFB fiber laser with intracavity frequency reference mechanism, by utilizing the beat note of dual modes inside the laser cavity as the laser wavelength drift reference signal. As one of the best results for the laser frequency stabilization without the external frequency reference, the outcome of this work presents a way to achieve a stable laser source as an alternative to the laser-locked to absorption line or FP cavity design with a simpler, lower cost feature, offering promising prospects for versatile applications outside of the laboratory.

The Pharaoh's snake experiment has been handed down for thousands of years, bringing a lot of Oriental mysteries. Its key technology is to establish a porous structure with expanded volume. Here, the Pharaoh's snake techniques have been used for producing rare earth-doped glass. The high-sodium precursor composed of SiO2-Na2CO3-P2O5-Er2O3 is prepared by the water-cooling method，which exhibits the phenomenon of Pharaoh's snake at 300℃ and forms fluffy Er-doped glass-sooting. Then the glass-sooting is crushed and further mixed with SiO2 thoroughly, and melted at high temperature to obtain a transparent Er-doped sodium silicate glass. There are abundant non-bridging oxygen in the high-sodium precursor, which can dissolve more rare earth elements, while the Er-doped sodium silicate glass has high silica content, strong chemical stability, and high practical value. The Er atoms in the raw material made by mixing glass-sooting and silica are physically uniformly distributed, which can reduce the Er atom clusters caused by the slow diffusion of ions in the high viscosity of the glass liquid during the melting process. Under the excitation of 980nm laser, Er-doped sodium silicate glass emits narrow bandwidth fluorescence at 1.5um, which has a good application prospect in L-band fiber amplifiers.

We report the luminance of 3D perovskite light emitting diodes can enhance by thermal annealing from 70 °C to 80°C. The encapsulated PeLED with Cs0.3MA0.7PbBr3-PEO film prepared under optimized heating conditions exhibited the change of the color purity at the initial lighting stage. This work demonstrates the importance of ambient temperature to the devices.

In optoelectronics and optical fiber communication, due to the wavelength coverage and the high sensitivity, InGaAs/InP avalanche photodiode (APD) has attracted more and more attentions. Herein, the InGaAsP/InP heterojunction was adopted in the multiplication layer. The absorption layer is composed of an intrinsic absorption layer and a depleted absorption layer. A new model of InGaAs/InP separate absorption, grading, charge and multiplication (SAGCM)-APD has been designed. The photocurrent, dark current and gain characteristics of the device were simulated. In addition, we also simulated the effect of heterojunction multiplication layer and charge layer on the punch-through voltage and break-down voltage of the device.

Over the past two decades, integrated photonics has achieved unprecedented advancement owing to the development of optical devices. Among those devices, waveguide Bragg gratings are widely used for optical true time delay and optical filtering. In general, the integration of WBGs faces several challenges, including high insertion loss and manufacturing difficulties. In this article we propose and experimentally demonstrated a novel waveguide Bragg grating design based on multimode waveguide. The proposed device features low overall insertion loss of 3.1dB.

Aluminum scandium nitride (Al_1-xSc_xN) optical waveguides with various geometric parameters and scandium (Sc) concentrations (x = 0, 0.09, 0.17, 0.32, 0.41) are investigated by numerical simulation. The waveguides are designed to operate at three near-infrared wavelengths of 940, 1550, and 2000 nm. The effective refractive indices and electric-field intensity of various optical modes for channel and rib waveguides are obtained. In addition, the impact of waveguide width as well as the slab thickness on the single-mode condition of the (Al_1-xSc_xN) waveguides are presented.

We present a DFB laser with extended direct modulation bandwidth based on groove-in-trench waveguide structure. The threshold currents of the fabricated DFB lasers are 8.0 mA and 19.1 mA at 25 °C and 85 °C, respectively. The 3dB bandwidths of the fabricated laser with an inject current of 60 mA is 29.2 GHz and 16.2 GHz at 25 °C and 85 °C, respectively. By etching groove-in-trench waveguide structure, we obtain a 3dB bandwidth enhancements of 3.5 GHz and 4.6 GHz at 25 °C and 85 °C, respectively. Transmissions of 25.8 Gb/s at 25 °C and 55 °C and 14.0 Gb/s at 85 °C with clear eye openings have been demonstrated.

We present a high-performance optical phased array on a double-layer Si3N4 platform, which takes the advantages of low macroscopic stress and low loss. We have performed both analytical and numerical simulations. In our design, the full width at half-maximum (FWHM) of the main lobe in transversal direction is 0.08°, while the FWHM in longitudinal direction is 0.09° due to the shallow etched grating antennas. The upward power is more than 50% in a broad wavelength range by optimizing the cladding thickness. The grating lobe suppression is reduced to 8.8 dB by using wide waveguide grating antennas. This optical phased array with high resolution and high efficiency will have a wide application in the fields of LIDAR and unmanned vehicles.

The miniaturization of optical devices is the development trend of optical products in the future. The WGM microcavity has been studied extensively in recent decades. We demonstrated a method of fabrication of high Q microtoroid cavity on a silicon wafer by the wet-etching without the dry-etching of poisonous XeF2. A 2.5 μm SiO₂ layer was fabricated by wet oxidation on the silicon wafer with a <100<. The main procedure was as follows: the standard photolithography technology was used to form disk on a <100< silicon wafer; tetramethylammonium hydroxide was used to corrode silicon; and the CO₂ laser was used to melt the disk and then obtained a microtoroid cavity with a microchip on the silicon wafer. We measured the transmission morphology characterization spectra of the microtoroid, and calculated the Q value.

This paper presents a laser protection idea to form a two-dimensional subwavelength metasurfaces structure with phasechange vanadium dioxide (VO₂) material. By using the phase change characteristics of VO₂, the signal light can be focused to the infrared focal plane at room temperature, and VO₂ undergoes a phase change under the action of a strong laser, which causes the spot on the focal plane to diverge, reducing the light intensity and energy density to protect the focal plane. The final imaging spot diameter of the metasurfaces designed in this paper is 4.4μm, which can intercept 76% of the incident energy from the outside after the phase change.

A high-precision three-gas detection system based on non-dispersive infrared (NDIR) technique was designed to accurately detect multiple gas concentrations in a complex environment. This system consists of an infrared source, a quad channel pyroelectric detector, a signal processing circuit and an optical gas chamber. A multiplexed digital lock-in amplification algorithm based on MCU was realized to improve accuracy, it has low cost of multiplex, there is potential to be applied to the measurement of multi-channel data. And a compact gas cell with the size of 40mmx110mmx22mm was designed, in which the average optical path length is 475mm. Initial measurement was done to one channel for SF6 gas concentration, and the feasibility of gas cell structure and signal processing circuit was demonstrated.

Based on the morphology of the fabricated polymer waveguide, we designed an optical waveguide model with a Gaussianshaped core, and simulated the coupling efficiency with the single-mode fiber and the loss of the bending waveguide at 1310 nm.

Poly(vinyl alcohol) (PVA) is a degradable, biocompatible and nontoxic polymer. The PVA functional films are flexible and suitable for use as flexible optoelectronic films. The transparent Ag nanowire/PVA films have received more and more attention due to their flexibility and abrasion resistance, compared with traditional indium tin oxide (ITO) films. However, the water resistance and manufacturing problems of the hybrid PVA films hinder their application. Here, we propose a simple method for fabricating hybrid PVA films, which can overcome the manufacturing problems of complex shapes and water resistance problems. The obtained Ag nanowire/PVA film is water-resistant, transparent, flexible and conductive, which is converted from hybrid hydrogel and driven by viscosity. Broadly, through this strategy of spraying Ag nanowire/PVA hydrogel precursors, the hybrid PVA films can be fabricated on the surface of three-dimensional molds with complex shapes, which has the potential for use in three-dimensional optoelectronic devices.

A 1×8 silicon optical phased array at 2 μm wavelength band is experimentally demonstrated. The optical phased array can achieve a steering angle of ±31° in the Ψ axis through the thermo-optic effect.

Bacterial vaginosis (BV) is one of the most common diseases for reproductive age women. BV is usually diagnosed by observing the color changes and ranges of various indicators in the sample, and then obtain further information. So, the identification of sample color is very important. In terms of the traditional testing method, the acquired sample image and the calculated RGB value are used as the basis for judging the condition. Since the RGB value fluctuates greatly due to the external interference such as light source, we propose a new testing method by using the H value in HSV (color model) as the basis for identifying the color of the sample, and develop a novel BV detector based on the Raspberry Pi hardware system and digital image processing algorithm, which realizes the extraction of the color information of the sample. The BV detector mainly encapsulates the Raspberry Pi, camera, LED light source and sample platform. They are all packaged in a homemade box with the small volume of 100 x 100 x 100 mm3, which makes the instrument portable. The BV detection application is designed based on Python programming language combined with OpenCV image processing database to realize Hough circle detection and Hue value of HSV color model for color detection. The experiment results show that the BV instrument has high sensitivity, high accuracy and good stability. It is a good early BV diagnostic instrument and has important application prospect.

Soliton microcombs, relying on the double balance of dispersion and nonlinearity, as well as gain and cavity loss, are formed in the mode-locked regime of a high-quality micro-resonator. Various soliton microcomb states can provide frequency components with different repetition rates and power, satisfying a variety of applications. Programmable switching of the soliton states increases operational flexibility. Here, we report the programmable switching of soliton microcomb states in a Si₃N₄ micro-resonator with anomalous dispersion by using an auxiliary laser. Red-detuned pump entrance is implemented to support the reliable judgement of state switching. Single-soliton state was realized in a small frequency tuning range of the auxiliary laser while multi-soliton states can be achieved under a wide range. The achievable soliton state number is related to the relative frequency position of the auxiliary laser. We can realize more number of the soliton states when the auxiliary laser is in the middle of the tuning range.

In general, the excess noise of avalanche photodiodes (APDs) will increase with incident mean optical power (Pin). However, it is found that the excess noise of InGaAs/InP APD decreases rather than increases with Pin in the case of high gain. The experimental and simulated results reveal that this phenomenon can be attributed to the nonlinearity effects, which results in the degradation of gain of APDs. And the nonlinearity effect is more significant with larger gain. Consequently, the excess noise will decrease due to the decreases of gain. For free space optical (FSO) communication systems which commonly operates the APDs at high gain, this discovery can be used to determine the optimum threshold of receivers to achieve the minimum bit error rate (BER).

The preparation of low-cost and large-area nanostructures is one of the frontier hotspots and difficulties in the field of nanotechnology. We propose a method for the preparation of nanostructures by using plasma to etch anodic aluminum oxide (AAO) membrane. The transmission characteristics of plasma particles in AAO nanopores are explored. And the precise control of the porous AAO structure is achieved. The nanostructure is successfully transferred to the LED chip, and the luminous efficiency is improved. These studies will provide a good theoretical and technical basis for the precise transfer of nanostructures and the low-cost preparation of large-area nanostructured devices.

Metal-organic frameworks (MOFs) in dye adsorption fields have been extensively studied due to it full of micropores. However, their micropores limit the materials, the speed of adsorption was also restricted. In this paper, we synthesized the single crystalline macro-microporous MOF through hard template method and compare its Rhodamine B adsorption speed with traditional microprous MOF’s, the result shows that the structure of macroporous significantly improved the dye adsorption ability of MOF.

Micro-laser-induced breakdown spectroscopy (μLIBS) has very important applications in elemental microanalysis of different samples. However, with the decreasing of ablated sample mass and plasma temperature, the detection sensitivity of μLIBS will decrease significantly. In order to solve this problem, target-enhanced orthogonal double-pulse laser-induced breakdown spectroscopy (TEODP-LIBS) using an aluminum target was investigated in this work. In the experiments, 532 nm laser pulses with 12 ns pulse width were focused on the brass sample surface by a 10x microscope objective to ablate the sample; time-delayed 1064 nm reheating laser pulses with 12 ns pulse width were focused on the surface of an aluminum target to produce target plasma. The ablated sample was reheated and further broken down by this orthogonal target plasma and enhanced atomic emissions of the sample elements could be observed. The emission spectra were recorded with a compact spectrometer coupled with non-intensified charge-coupled device (CCD) detectors. The intensities of the optical emissions of the sample elements in μLIBS, ODP-LIBS as well as TEODP-LIBS were compared. Up to 3 orders and 16-folds signal enhancement have been observed in TEODP-LIBS if compared with μLIBS and ODP-LIBS, respectively. It is demonstrated that TEODP-LIBS is able to give much higher enhancement factor on the signal intensity than ODP-LIBS. TEODP-LIBS is able to significantly improve the detection sensitivity of μLIBS under minimal sample ablation and find important applications on the elemental microanalysis of different samples.

The spatiotemporal coupling (STC) distortion of large aperture ultra-high peak power laser will stretch the focused pulse and reduce the peak power. In order to accurately characterize the laser field distribution and compensate the spatiotemporal coupling distortion, a single-frame measurement of full three-dimensional STC distortion based on carrier frequency distinguished spectral interferometry (CFDSI) is proposed. The setup requires only a slit array attached in front of an imaging spectrometer. The whole process of CFDSI is simulated in this study, and the simulation results prove its correctness and effectiveness.

Femtosecond laser direct writing (FLDW) of waveguides in transparent glass have found great use in photonic integration and quantum simulations. To fully take advantage of FLDW, much attention has been paid to exploring high-performance waveguides. The circular aperture, as a diffraction element in the lens focusing system, can strongly affect the intensity distribution at the focus. Here, we theoretically analyze the influence of a circular aperture on the focal volume of a collimated Gaussian beam and experimentally investigate the performance of FLDW of waveguides in a fused silica substrate with using a circular aperture. Waveguides with low propagation loss of 0.33 dB/cm, highly symmetrical mode field at 633 nm have been successfully prepared by using the circular aperture of diameter 5.5 mm. Moreover, the aspect ratio of FLDW of waveguide cross-section can be tuned by changing the diameter of the circular aperture, resulting in the manipulation of the guiding mode profile.

With the discussion of sixth generation gradually raising the curtain, the requirement to further expand the bandwidth makes the optical wireless communication one of the best alternatives. However, the strong atmospheric turbulence under the sunlight limits the application of the technique in the common environment. Therefore, in this paper, we study a kind of partially coherent beam (PCB), namely Bessel-Gaussian Schell-model (BGSM) beam, in terms of its propagation characteristics in atmosphere, and then construct a spacing division multiplexing (SDM) scheme based on BGSM beam. Based on the results, the BGSM beam has a stable distant annular facula that its radius is independent to the random medium, and it has wonderful atmosphere-resistance that even considering the intensity fluctuation from the PCB source, it shows larger signal-to-noise ratio (SNR) than its coherent counterpart in the strong turbulence. When several coaxial BGSM beams with different coherence distribution propagate through a space, the difference of their ring’s radius makes them illuminating on different circles. Deploying the diversity reception, the source scintillation is mitigated so that every channel could afford stable transmission. Under the different turbulence condition, the SDM scheme at least double the total capacity comparing to the traditional communication scheme.

In this paper, recent work on picosecond and nanosecond hybrid laser treatment of mechanically sawed single-crystal silicon wafer is presented. Surface morphology, surface roughness and phase development has been analyzed by 3D laser scanning confocal microscope (LSCM), X-ray diffraction (XRD), and scanning electron microscope (SEM). Results show that as-received surface defects including SiO₂ layer and saw-mark defects have been significantly reduced, while average surface roughness has been decreased. No obvious damages such as micro-cracks and micropores have been observed at the laser-treated surface. Moreover, residual stress and electrical resistivity of laser-treated surface has been measured, respectively. The insights obtained in this work provide a facile method to improve surface quality of mechanically machined silicon wafer.

We built a 300G terahertz (THz) frequency modulated continuous wave(FMCW) imaging system. This paper describes the construction and imaging experiment of a FMCW system with a sweep bandwidth of 275~325GHz. Quasi-optical module of the system can focus the spot radius of the system from 16.35 mm to 7.61 mm. The signal-to-noise ratio and resolution of the system were greatly improved. At the same time, the cage structure design of industrial application-grade lens group is implemented, which greatly increases its applicability. We conducted both one-sided and three-dimensional imaging experiments on the built imaging experimental system. The results show that the resolution of the designed imaging system can reach 3 mm, which is of tremendous value for the application of THz nondestructive testing.

A wideband programmable linearly frequency modulated (LFM) signal is highly desired in modern radar systems to adapt to variable environments and achieve high detection resolution. However, conventional digital microwave generation has restrictions on operation band and bandwidth. Current optical microwave generation has provided solutions to the dilemma of electronic devices, meanwhile arising new problems like insufficient time-bandwidth product and dependence on high-frequency or high-rate RF sources. Here, utilizing heterodyne-beating two phase-locked lasers, we present a new LFM signal generation method with no aid of high-frequency or high-rate electronics, featuring simple structure, large bandwidth and adjustable parameters. A frequency-swept laser (FSL) and a frequency-fixed laser (FFL) combined with a voltage-controlled oscillator are phase locked to the same oscillator to reduce phase fluctuations and employed for heterodyne-beating. An LFM waveform with an instantaneous bandwidth of 7.3 GHz cross X and Ku band is developed. The reconfigurable capability is also investigated, the bandwidth, central frequency and pulse width of the LFM signal are programmed by merely adjusting the central frequency of the FFL, voltage amplitude and the period of a low-frequency driving voltage signal driving the FSL. Measured results validate the effectiveness and prospect of the approach.

As an improvement of the traditional recurrent neural networks (RNN), the reservoir computing (RC) only needs to train one output connection weight matrix linearly, which greatly reduces the number of machine learning network calculations. The optoelectronic RC can be realized with a delay feedback loop composed of optical and electrical devices. It has the advantages of lower power consumption and faster speed than the all-electric RC scheme. At the same time, it is easier to be controlled than the all-optical RC scheme. In this paper, we propose to employ the optoelectronic RC to process radar signals to distinguish different persons in the indoor environment. The radar signal required for the simulation is referred from the IDRad data set, which contains the echo signals of the frequency modulated continuous wave (FMCW) radar, and five persons of different ages are free to move around in the room, which is close to the real scene. First, the echo signal is processed and the micro-Doppler features are extracted, and each frame corresponds to a row vector. Then, this vector is used as the input signal of the optoelectronic RC. We numerically studied the impact of parameters such as the size of the RC and the regularization coefficient in the system. Finally, the classification accuracy of five targets reaches 87%.

A linearization scheme in the digital domain for photonic sampling analog-to-digital converter (PS-ADC) is proposed and experimentally demonstrated, where a single-output Mach-Zehnder modulator (MZM) is used for photonic sampling instead of a dual-output MZM (DOMZM) in the traditional schemes. After frequency response calibration of the sampled signal in the digital domain, the optimal direct current (DC) component and the coefficient of sine function are found, and arcsine algorithm is performed to implement the linearization of PS-ADC. The theoretical results indicate that, compared with the differential and arcsine operation method generally employed in PS-ADC, the proposed scheme is facile to implement and decreases the system overhead. The feasibility of the scheme is verified by simulation and experiment. In the proof-of-concept experiment, for a single-tone microwave signal at 100 MHz with a modulation index of 0.45π, the second-order harmonic is suppressed below the noise floor, the third-order harmonic suppression ratio is enhanced by 17.14 dB, and the significant improvement in SINAD is equal to 7.91 dB.

Optical beamforming network is the core part of microwave photonic phased array radar. In this paper, the principles and features of different optical beamforming network technologies are proposed and analyzed, which provide certain theoretical support for applications in engineering practice. The future development of research work in this field is finally given and prospected.

Recently, deep learning methods have revolutionized the design of nanophotonic devices, which provides a new way to efficiently design nanophotonic devices. Here, we demonstrated a deep learning method using attention mechanisms to inverse design nanophotonic devices, the mean relative error of the predicted value can be as low as 4.1% or less. Using the encoder part of Transformer, the long sequence of spectral data can be mapped to the structural parameters of the nanorod hyperbolic metamaterial. The inverse design model based on the attention mechanisms is good at processing sequence data and can be calculated in parallel, which is an effective way to design nanophotonic devices.

Different from the quenching effect of conventional dyes, aggregation-induced emission (AIE) dyes radiate fluorescence with the increase of aggregation state, which is a new application in optical storage. In order to increasing the fluorescence contrast of information recording point, a higher writing beam is required. It means that the fluorescence contrast of information point is not excellent at low writing laser power, which undoubtedly improves the bit error rate of information readout. To circumvent the above problem, we doped Mg^{2 +} ions in tetrastyrene (TPE) resin and found that its fluorescence intensity was enhanced. Under this feature, we use the same writing power and find that the fluorescence contrast of its information is also significantly enhanced. Our results provide a way to realize super-resolution recording for AIE optical storage, and to explore the use of AIE dye doped photopolymers chemical sensors.

A tunable dual-gas sensor based on VO₂ is proposed, and the metasurface is composed of a multi-layer metal-dielectricmetal (MDM) structure. The first to six layers of the structure are VO₂ cylinder, methane sensitive film, VO₂ film, gold square ring, hydrogen sensitive film, and gold film. The conductance coupling between the metal structures can be manipulated by the metal-insulator phase transition of VO₂ to change the LSPR resonance mode. The transformation realizes active tunable dual-gas detecting of the methane and hydrogen, and the effects of structural parameters and polarization mode on the frequency response characteristics of the structure are investigated respectively. Subsequently, a theoretical study of the active adjustable dual gas sensor was carried out. When the temperature exceeds the phase transition temperature of VO₂ (T<68℃), VO₂ exhibits metallic properties and excites resonant coupling at 1647.4nm. At this time, methane-gas detection is realized and the absorption rate of the sensor reaches 92%, which is not only because of the VO2 cylindrical surface resonance but more electric energy is localized in the methane-sensitive film. The sensor realizes hydrogen detection when VO₂ is in an insulated state (T≤68℃), the incident light penetrates the upper three-layer structure and matches the plasma frequency of the lower three-layer MDM structure to excite resonance at 2191.4nm. However, the energy of the incident light is lost through the upper three-layer structure, which causes the absorption rate of the sensor to be only 83%. In addition, the influence of the external dielectric constant and structural parameters on the sensing characteristics are analyzed to obtain the optimal sensing performance, where the sensitivity of methane is 7.46nm/% and the sensitivity of hydrogen is 1.6nm/%. This conclusion is conducive to the design of active adjustable sensors and has many potential applications in the field of detection.

It has become an important application of microwave photonics in radar system to exchange information between radar antenna RF front-end and information processing terminals by optical interconnection technology. With the continuous improvement of radar system integration, the optical exchange between multilayer chips also faces higher challenges, especially the coupling density and position arrangement between chip waveguide themselves or between the optical fiber and chip waveguide. In this paper, a kind of integrated optical interconnection technology was proposed to help information exchange between multilayer chips based on evanescent coupling with taper structure. By the finite difference time domain (FDTD) algorithm, simulations were carried out and the results indicate that the insert loss could be restrained to 3.5 dB for the optical interconnection between different lay chips which have a gap of more than 1 micron. Besides, the optical interconnection could support high density distribution and flexible position arrangement for the optical coupling.