This PDF file contains the front matter associated with SPIE Proceedings Volume 13233, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

This paper introduces two time-frequency analysis schemes based on nonlinear semiconductor laser dynamics reported recently by us. The key to the two schemes is the nonlinear period-one (P1) semiconductor laser dynamics. By injecting an optical signal with linearly varying intensity over time into a semiconductor laser, a wideband frequency-sweep optical signal is generated via the P1 oscillation. Subsequently, the wideband frequency-sweep optical signal is modulated by the Signal Under Test (SUT), generating multiple frequency-sweep optical sidebands that are directly associated with the SUT frequency. Then, an optical narrowband filter is used to process these optical sidebands to implement the frequency-to-time mapping and the final time-frequency analysis. The narrow transmission peak in the notch of a phase-shifter fiber Bragg grating and the Stimulated Brillouin Scattering (SBS) gain spectrum are used as the optical narrowband filter, respectively. The former features a simple system structure and easy implementation but its bandwidth is hard to adjust. The latter, because its bandwidth is easy to manipulate, can meet the needs of performance optimization under different sweep chirp rates. To solve the problem of limited measurement resolution caused by the instability of P1 oscillation, an optoelectronic feedback loop is employed to stabilize the P1 oscillation to improve the stability and performance of the system. Furthermore, the nonlinearity of the generated frequency-sweep optical signal is compensated through pre-compensation or post-compensation. Using the proposed system, the time-frequency information of SUTs in a 4-GHz bandwidth is acquired.

In this paper, we propose an Optoelectronic Oscillator (OEO) based on a Directly Modulated Laser (DML) to generate multi-frequency microwave signals. The proposed OEO features in a DML with no external modulator in the loop, an electrical mixer to provide the multi-frequency injection signals, and a two-channel electrical filter bank to choose the desired oscillation modes. The generated multi-frequency microwave signals have excellent performance in the Side Mode Suppression Ratio (SMSR), phase noise, tunability and coherence. In the proof-of-concept experiment, triple-frequency microwave signals are demonstrated with the frequency tunability of 8 - 12 GHz, and the SMSR and phase noise can be up to 53 dB and -120 dBc/Hz @ 10 kHz, respectively. Moreover, quintuple- and septuple-frequency microwave signals are also successfully generated.

Fringe projection profilometry (FPP) is a high-precision, non-contact measurement technique. The quality of 3D reconstruction largely depends on the projection quality and the number of phase shifts and frequencies. Traditional MEMS projection methods project fringes only during the forward scan, limiting projection light intensity as they do not utilize the reverse scan. To address this, a high-quality fringe projection system is developed using an FPGA and a uniaxial MEMS scanning mirror. The method projects 8-bit fringe patterns based on angle interval signals and uses both forward and reverse scans. By projecting patterns in both directions and reversing the forward pattern during the backward scan, the projection light intensity is effectively doubled compared to unidirectional methods. This bidirectional scanning approach projects the same pattern during both the forward and backward scans, doubling light intensity and improving the Signal-to-Noise Ratio (SNR) of captured images, thus enhancing the reconstruction accuracy of the MEMS-based system.

Microwave photonic signal processing such as microwave frequency measurement and temperature sensing has been widely studied due to its advantages such as large instantaneous bandwidth, high resolution, flexible reconfigurability as well as immunity to electromagnetic interference. In this paper, we review our recent works about microwave photonic signal processing based on parameter-to-time mapping, where the parameters under test, such as the frequency or temperature, are mapped to the time interval of the output pulses. Parameter-to-time mapping relationship is therefore established, and the parameter can be measured by using a low-speed time-domain acquisition equipment. The microwave photonic signal processing schemes based on parameter-to-time mapping feature low-cost and high resolution, which have great potential in applications such as radar, electronic warfare and metrology systems.

We propose a novel Polarization-Dependent Loss (PDL) measurement method to achieve optical device polarization characterization. The method utilizes high-fineness frequency sweeping based on Microwave Photonics (MWP) to achieve high frequency resolution. Theoretically, a sub-Hz frequency resolution is available. In the experiment, the stimulated Brillouin scattering (SBS) in a 5-km single-mode fiber serves as the device under test (DUT). The PDL is measured with a frequency resolution as high as 100 kHz over a frequency span of 400 MHz, demonstrating the advantages of high frequency resolution.

In this paper, we propose and demonstrate a Frequency Modulated Continuous Wave (FMCW) laser source realized through sideband modulation and four-wave mixing (FWM). A silicon waveguide, featuring a reverse-biased P-i-N junction, is designed to excite FWM process. The FWM process in silicon waveguide expand threefold frequency sweeping span to 6 GHz, thereby enhancing spatial resolution to 2.5 cm. The original tuning range of 2 GHz and tuning rate of 0.2 GHz/s is multiplied by three times to 6 GHz and 0.6 GHz/μs respectively. The frequency-modulated light source exhibits excellent linearity, low noise, narrow linewidth, and fast tuning rates, which are critical attributes for modern electrical systems.

A weighted K-means algorithm is introduced to improve the performance of the FSO-based KK receiver under lower CSPR and large atmospheric turbulence, the numerical simulation results show that by using the weighted K-means algorithm, a 1dB CSPR reduction is obtained when the FSO link length is extended to 3000m, compared to the conventional hard-decision scheme.

Microwave photonics, as an interdisciplinary filed, has inherit advantages, such as large operating bandwidth, high frequency band, light weight, high transmission speed, flexible tunability, and immunity to electromagnetic interference compared to traditional electronic methods. Thanks to these merits, microwave photonics has attracted attention from considerable researchers and been extensively studied. In this paper, we review our latest works which focus on the generation of high-frequency, broad-bandwidth radio frequency (RF) signals and the accurate measurement of multiple parameters. These schemes fully leverage the advantages of microwave photonics, and might be utilized in radar, electronic warfare, and communication systems, offering enhanced performance, flexibility, and reliability in a compact and lightweight configuration.

In this work, we present the simulation and analysis of an oxide-confined Vertical-Cavity Surface-Emitting Laser (VCSEL) using the Finite Difference Frequency Domain (FDFD) microcavity model, integrated within the Crosslight’s PICS3D simulation package. By utilizing a full vectorial microcavity approach, both fundamental and higher-order optical modes are accurately captured, offering detailed insights into the effects of key structural parameters of the optical cavity. This study focuses on the impact of the oxide layer’s position and thickness on mode behavior, lasing mode selection, and threshold current in large-aperture VCSELs. The optimized VCSEL design achieves a threshold current of 0.7 mA and a far-field divergence angle of approximately 8°.

High-accuracy calibration of uniaxial MEMS-based systems is essential for achieving precise 3D reconstructions because the calibration results will directly affect the accuracy of 3D reconstruction. Calibration data consists of two parts: absolute phase and corresponding 3D coordinates. However, due to the unstable motion of MEMS scanning mirrors and defects in the calibration board, the obtained calibration data may contain errors. These erroneous data points can significantly reduce the calibration accuracy of MEMS systems. To address this challenge, we propose a high-accuracy global calibration method based on an outlier removal strategy. First, the proposed method obtains calibration data using a calibration board with a checkerboard or dot matrix pattern. Then, the system is calibrated using the improved RANSAC algorithm. During each iteration, the fitting residual for each calibration data point is calculated based on the calibrated model parameters. The optimal calibration model is iterated based on minimizing the total fitting residuals. In this process, outliers are removed as they would lead to significant calibration errors. Experimental results show that the proposed method effectively mitigates the impact of negative factors on system calibration, such as the unstable motion of the scanning mirror. The outlier removal mechanism enhances the accuracy of system calibration, thereby achieving accurate uniaxial MEMS-based reconstruction.

To mitigate the risk of eavesdropping and subsequent data leakage, we introduce an innovative encryption methodology leveraging Phase Ambiguity (PA)-based chaotic encryption. The PA chaotic encryption algorithm is designed to effectively encrypt the original signals without compromising the transmission performance of the KK receiver.

The main purpose of this paper is to achieve performance analysis and improvement in Microcomb-Based Microwave Photonic System (MBMPS). Specifically, we first derive the formula of electro-optic modulation in microwave photonic system with multiple wavelength channels, and then analyze the Spurious-Free Dynamic Range (SFDR) of MBMPS in theory. Meanwhile, we proposed an efficient approach to significantly enhance the working bandwidth of MBMPS, which is obtained by incorporating microcomb wavelength interleaving technique and high-performance electro-optic modulation. In the experiment, we investigate the process of electro-optic modulation in multiple-wavelength microwave photonic system, and measure the SFDR performance of single wavelength channel in MBMPS.

This work theoretically explores the impact of external carrier noise from pump source on the optical noise characteristics of Quantum Dot (QD) lasers. The investigation includes simulations of the effects of a normal pump with a Gaussian carrier distribution and a quiet pump with a sub-Poisson carrier distribution on the spectral linewidth and Relative Intensity Noise (RIN). The results reveal that the spectral linewidth and RIN are significantly reduced when using a quiet pump compared to a normal pump across bias currents ranging from 1.5 to ten times the threshold currents, attributed to the lower carrier noise level of the quiet pump. At six times the threshold current, the spectral linewidth of the quiet pump decreases to 339.8 kHz, approximately half of that observed with normal pump, while the RIN value improves from -142.4 dB/Hz to -169.5 dB/Hz. Moreover, due to the larger external carrier noise of the normal pump at higher currents, this disparity in spectral linewidth and RIN between normal and quiet pump states becomes more pronounced, with the QD laser under normal pump exhibiting a broadening phenomenon that does not occur with the quiet pump. At ten times the threshold current, the spectral linewidth under normal pump broadens to 536.0 kHz, while under quiet pump, the spectral linewidth continues to decrease to 130.8 kHz, and the RIN value decreases from -145.5 dB/Hz to -172.4 dB/Hz. This work thus paves the way for the application of QD lasers in next-generation photonic integrated circuits by effectively reducing both the spectral linewidth and RIN of these optical sources through a straightforward and manageable strategy.

High power large-scale single junction 808nm VCSEL arrays were fabricated at a chip size of 5.1mm×6mm with regular 100µm thickness substrate and packaged on commercial AlN submounts. The CW optical power was tested up to 100W from a single chip with maximum PCE of 44% and slope efficiency of 1.2W/A. The QCW optical power was tested up to 270W from a single chip with maximum PCE of 50% and slope efficiency of 1.35W/A. This is one of the best performances for high power VCSEL chips for commercial delivery. Side-pumped Nd:YAG laser was designed with these VCSEL chips and experiment was proceeded. High optical-to-optical pumping efficiency of 45% was calculated and the implied Nd:YAG stored energy was up to joules level. These experiments showed great potential for the high power VCSEL chips for Nd:YAG laser pumping and also offered great possibility for volume production and commercial delivery in the near future.

Prediction of optical chaos has been a key enabler in fields including random number generation and private secure communication. Hereby, we propose an Extreme Learning Machine (ELM) based approach to forecast the chaotic phenomenon of semiconductor lasers effectively. Then, by taking advantage of the features of the ELM, we propose to use a circulant structure for the input weight matrix and the Fast Fourier Transform (FFT) for implementation, leading to significant computational complexity reduction. To meet the the need of dynamic forecasting with less samples, an adaptive ELM is introduced for continuous prediction of optical chaos. To achieve this, recursive least square is employed to update the ELM with chaotic data arriving one-by-one or batch-by-batch for dynamic prediction. Simulation results demonstrate the proposed methods can forecast the optical chaos effectively in dynamic forecasting scenario.

The study presents the design, fabrication, and testing of the 4th-order surface grating laser with a focus on achieving stable single-mode emission. This approach contrasts with traditional high-order surface gratings, aiming to minimize loss and enhance the yield of single-mode operations. The laser device showcases a remarkable single-mode performance, with an injection current of I_FP = 57 mA and I_Grating = 20 mA, achieving a side mode suppression ratio of 56.97 dB. The threshold current remains around 11 mA, reaching a peak power output of 5 mW. The experimental results highlight the potential of using low-order surface gratings for efficient single-mode lasers, streamlining the fabrication process while enhancing device performance.

We design and demonstrate a deformed-square-FP coupled cavity laser that achieves spontaneous chaotic output through the mode coupling between whispering-gallery modes and FP modes. Our lasers are fabricated using i-line projection photolithography, avoiding the need for complex systems or grating fabrication. They have the advantages of a compact size and a simple structure. By connecting waveguide at the vertex of polygonal microcavity, the chaotic output power of microcavity laser is significantly improved, which can reach more than 1mW. The chaotic states can be observed within a current range of 5mA, and its maximum chaotic bandwidth reaches 9GHz. This design provides a new solution for increasing the output power of chaotic microcavity lasers in practical applications.

In the fields of fibre-optic communication, LiDAR, gas sensing and biomedical imaging, temperature fluctuations affect the wavelength and output power of Vertical-Cavity Surface-Emitting Lasers (VCSELs), thereby reducing system stability and measurement accuracy. This study proposes a VCSEL temperature control system based on the ZYNQ platform (Zynq-7000 All Programmable SoC), aimed at achieving high precision and stability in temperature management. The system integrates a Thermoelectric Cooler (TEC) and a Negative Temperature Coefficient thermistor (NTC), utilizing ZYNQ’s reconfigurable logic and processing units for temperature monitoring and control. A Proportional-Integral-Derivative (PID) control algorithm is implemented for real-time temperature adjustment. Compared with traditional temperature control schemes, this system offers significant advantages in hardware integration and control flexibility. Experimental results show that the ZYNQ-based temperature control system excels in temperature stability and control precision, effectively mitigating the impact of temperature drift on VCSEL performance.

In this paper, we propose a structure for flip-chip bonding of the transmission line chip, enabling the connection of high-speed optoelectronic chips with other high-speed chips or RF connectors. The simulation results demonstrate that this structure could achieve excellent RF transmission performance and high process tolerance within the range of 10 MHz to 67 GHz.

The pivotal role of Photonic Integrated Chips (PIC) has become increasingly prominent in modern telecommunications, especially in data center interconnects and high-speed optical networks, which demand enhanced energy efficiency from these devices. Researchers continually strive to explore more efficient algorithmic approaches to meet this power consumption challenge. The Principal Component Phase Estimation (PCPE) algorithm stands out due to its inherent advantage of low computational complexity, low cycle-slip rate and better Mutual Information (MI) performance, making it a promising solution for reducing Digital Signal Processing (DSP) chip operational energy. However, limitations exist in current PCPE algorithm when dealing with specific modulation formats like odd-bit QAM, thereby limiting its full application potential. Addressing this issue, this work focuses on proposing an innovative Element-wise Addition pre-Processing (EAP) scheme that enhances the clarity of principal component in odd-bit Quadrature Amplitude Modulation (QAM) signals at the phase recovery stage, subsequently improving the accuracy of the PCPE algorithm. Simulation results demonstrate improved mutual information rates of 0.13 bits/symbol for 32QAM and 0.54 bits/symbol for 128QAM systems after applying the proposed solution. These findings indicate that the suggested EAP method strengthens the PCPE algorithm's performance in handling odd-bit QAM signals, broadening its application scope, and paving the way towards more energy-efficient and high-performance solutions in the field of optoelectronic chips.

In this paper, we present an investigation into the interaction between Probabilistic Shaping (PS) techniques and frequency-domain dispersion estimation algorithms within coherent Digital Signal Processing (DSP) chips for Photonic Integrated Circuits (PIC). For the first time, we analyze how PS affects the performance of dispersion estimators, revealing that increased shaping factors lead to flatter slopes around the optimal value in the frequency domain auto- correlation function used as a cost metric, thus complicating accurate dispersion parameter estimation and potentially causing severe erroneous estimations. Through Monte Carlo simulations, we assess the impact of dispersion estimator errors on the mutual information achieved by different shaped PS-64QAM signals, demonstrating that under certain conditions, the performance degradation resulting from the incompatibility between PS and dispersion estimation can severely impair the shaping gain provided by the PS technology. Our study underscores the need for future research in coherent DSP to address the compatibility issues between PS and dispersion estimation algorithms, either by developing robust new dispersion estimation methods resilient to PS or refining the probability distribution models of PS to minimize the influence of signal variations on estimation accuracy. This work provides valuable insights for enhancing the adaptive capabilities of photonic chips across diverse service scenarios.

Interband Cascade Lasers (ICLs) subject to optical feedback can produce periodic oscillations. In this work, we investigate experimentally the influences of current modulation on nonlinear dynamics of an optical feedback ICL operating at period-one (P1) oscillation. By varying the power and frequency of current modulation, we can examine the variations in the time series, power spectrum, and phase portrait of the laser output resulting from the introduction of current modulation. The results show that, the P1 fundamental frequency of the optical feedback ICL exhibits a frequency drift after introducing a current modulation with a relatively low modulation power. When the modulation power is set at a relatively high level, the optical feedback laser may behave the locking phenomenon, period-three (P3) state or period-two (P2) state under a modulation frequency close to theP1 fundamental frequency of the optical feedback ICL.

High-temperature operating characteristics and polarization stability are important for VCSEL as an atomic clock light source. In this study, the polarization-stable single-mode 795 nm VCSEL with anisotropic aperture was successful fabricated by controlled the asymmetric airflow distribution and the different oxidation rates of the crystal direction. The oxidation of different crystal direction of asymmetric oxidation aperture with time is summarized. The surface electric fields of the traditional circular oxidation aperture VCSEL(C-VCSEL) and diamond shape oxidation aperture VCSEL(D-VCSEL) with different aperture sizes are investigated by simulation, and then the cause of the anisotropy of D-VCSEL is explored. The special anisotropic oxidation aperture of the device makes it have stable polarized characteristics. The demonstrated D-VCSEL with dimensions of 3.6 μm × 4.8 μm, achieving an orthogonal polarization suppression ratio (OPSR) exceeding 30 dB while maintaining low threshold and high single-mode output even at temperatures up to 80 °C.

The thermal crosstalk effect severely limits the application of Vertical-Cavity Surface-Emitting Laser (VCSEL) array. In this paper, using the high transparency and ultra-fast mobility of graphene, we have designed a VCSEL array with graphene electrode (Gr-VCSEL array). By avoiding lateral transport of current, the series resistance and self-heating of Gr-VCSEL are reduced. Compared with traditional VCSEL array, the 10×10 Gr-VCSEL array achieves a 20.6% reduction in series resistance and a 26% decrease in red-shift rate of wavelength. Benefit by the high thermal conductivity of graphene electrode, the thermal resistance of Gr-VCSEL array is reduced by 7.8%. This structure has excellent thermal properties and is not limited by wavelength, which provides a new method for the development of VCSEL array.

Reserve computing, inspired by the brain's information-processing capabilities, is well suited for tasks that deal with time-related data. Recently, optoelectronic reservoir computing using a semiconductor laser with optical feedback and optical injection as single nonlinear node architecture has gained significant attention. By introducing mask preprocessing into the data, machine learning methods that leverage the nonlinear dynamics of semiconductor lasers for information processing have become widely recognized. However, while the reservoir computing structure appears simple, it is challenging to understand the data variations. In this paper, we conduct numerical simulations of the model, simply expound on the data flow within the system, and complete the task of short-term chaotic time-series prediction.

Reservoir Computing (RC) is an Artificial Neural Network (ANNs) that simulates human brain behavior and thinking. As a new type of ANNs, RC does not require training for its reservoir layer, only for the output weights. This simple training method enables RC to be implemented in a physical way. This article successfully builds a time-delayed optical feedback RC system based on semiconductor lasers using the nonlinear characteristics of optics. The system adopts the idea of time division multiplexing, uses the delay loop of optical feedback to construct a reservoir, and sets up a large number of virtual nodes in the feedback loop to replace traditional reservoir nodes. Finally, we successfully implemented spoken digit recognition tasks through this RC system.

We implement sub-Hz-level instantaneous linewidth (70dB linewidth compression) laser source by self-injection locking to a high-quality-factor (⪆10e8) WGM microresonator module with locking time of more than 24 hours. We independently developed a few mode, high-quality-factor micro-cavity module which directly integrated with DFB chip. The entire optical module can be packaged to enhance robustness, making it truly commercialized and compatible to industrial optical systems.

With the continuous development of communication systems, the demands on optical transmitters have progressively increased. There is an increasing expectation for these transmitters to be more compact while achieving low power consumption, broad bandwidth, and high environmental stability. Lithium Niobate on Insulator (LNOI) modulators are well-suited to meet these requirements due to lithium niobate's large electro-optical coefficient and the ridge waveguide's strong light confinement, which enables a smaller chip size. In this work, we initially designed the LNOI modulator structure using numerical simulation, and then proceeded with fabrication. After that, we developed a package that integrated the modulator with a III-V semiconductor laser diode via lens coupling and incorporated a Thermoelectric Cooler (TEC) to enhance temperature stability. The small signal test result shows that we have successfully fabricated a transmitter with a 3-dB bandwidth of 44.3 GHz.

In this paper, the light source is fiber coupled semiconductor laser. The lens system is used to image the image of the fiber end face on the heated object, and the focusing range is 6.5-70mm. Then the trajectory is optimized in the non-sequential mode of ZEMAX. The system uses five lenses and uses a cam structure to achieve zoom. A laser homogenizing zoom system with adjustable spot size in the continuous range of 12mm-151mm at a distance of 1.5m was designed, and the mechanical structure was designed. The system structure is simple, and the uniformity can reach more than 86% in all spot size ranges

Based on chaos synchronization between two 1550 nm response vertical-cavity surface-emitting lasers (R-VCSELs), we propose and numerically investigate a bidirectional dual-channel chaotic secure communication system. Under delayed dual-path chaotic signal injections from the injection VCSEL (I-VCSEL) with polarization-preserved optical feedback, a driving VCSEL (D-VCSEL) can generate an optimized chaotic signal, which can drive two R-VCSELs to output polarization-resolved chaotic signals with wide bandwidth about 35 GHz and low TDS below 0.1 in a relatively large parameter range. Moreover, high-quality isochronal chaos synchronization between the corresponding linear polarization components of two R-VCSELs can be achieved. In contrast, the synchronization quality between D-VCSEL and arbitrary one R-VCSEL is inferior. On this basis, through the polarization-division-multiplexing technique in conjunction with the chaos modulation (CM) method, this proposed system can realize security-enhanced bidirectional dual-channel message transmission of 30 Gbps bipolar non-return-to-zero signals over a 140 km fiber link with Q-factors above six. After adopting four-level pulse amplitude modulation, 60 Gbps signals can be successfully transmitted over a 60 km fiber link with Bit-Error-Rates (BERs) below the hard-decision forward error correction (HD-FEC) threshold of 3.8×10^-3.

Phase noise refers to the random phase fluctuation in the laser system. Calculating laser phase noise requires large datasets, leading to inefficiency. For optimizing, we apply I/Q demodulation and multi-threading with window functions, discrete Fourier transforms and cross power spectral density. Additionally, the cross power spectral density enable to reduce the impact of measurement system. This method converts the real signal into a complex one via the Hilbert transform, removes the carrier with linear fitting, and calculates phase noise through cross power spectral density.

Absolute distance measurement is increasingly in demand in applications such as large-scale equipment manufacturing and satellite formation flying. Multi-wavelength interferometry is an effective method for achieving high-precision, large-range absolute distance measurement. Excess fraction method is the basic approach to solve the distance in multi- wavelength interferometry, but this method requires a large number of comparisons of fractional phases to obtain the integer phase of each wavelength, so thousands of calculations are required. The proposed solution in this paper involves directly determining the fractional fringe of the synthetic wavelength using the fractional fringe of each individual wavelength, establishing the integer fringe for each wavelength and the final distance measurement result.

Tapered semiconductor lasers have gained significant attention for their capability to achieve both high power and high beam quality. These lasers consist of an index-guided ridge waveguide and a gain-guided tapered amplifier. By implementing deep etching in the ridge section and introducing on-chip compressive stress in the tapered amplifier, the degree of polarization and beam quality of the laser output are improved. Combining the methods above, the polarization mismatch between the ridge and tapered sections is addressed and amplification efficiency is enhanced. The fabricated InGaAs/AlGaAs compressive strain single quantum well laser, emitting at a wavelength near 1μm, achieves continuous wave output of 11.57 W at tapered current of 14 A, with a degree of polarization exceeding 90%.