This PDF file contains the front matter associated with SPIE Proceedings Volume 12972, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

A photonic integrated wireless sensing and communication (ISAC) system with photonic frequency multiplication and frequency conversion of orthogonal frequency division multiplexing (OFDM) signals is proposed and demonstrated. We designed and simulated a 16QAM-OFDM modulation photonic ISAC system, which is operated at 90 GHz with a bandwidth of 12.5 GHz. High-speed communication with a bit rate of 50 Gbit/s and high-resolution sensing with a range resolution of 1.2 cm is achieved. In addition, the OFDM ISAC system has the characteristics of a low sampling rate and high accuracy due to the use of optical frequency conversion.

The measurement of refractive index plays a crucial role in biosensing. This paper proposes a novel solution for refractive index sensing by utilizing seven-core fiber spatial multiplexing to receive the spectrum of a no-core fiber. Compared to existing high-sensitivity fiber sensing structures like core offset and polishing, this solution offers the advantages of easy production and a simplified process. In terms of spectral demodulation methods, this solution employs deep neural networks to replace the traditional approach of tracking spectral peaks or troughs. By utilizing the entire spectrum information, the accuracy of spectral demodulation is significantly improved. Additionally, the use of seven-core fiber with spatial multiplexing characteristics allows for the reception of a larger amount of information compared to single-mode fiber, thereby further enhancing the refractive index sensing capability. The results demonstrate that this solution achieves a remarkable refractive index sensing accuracy rate of 2.25×10^-5.

With the development of observation satellite, precision lathe and lithography, the demand for high-precision three-degree of freedom (3-DOF) angle measurement instruments is becoming increasingly urgent. Laser measurement has the advantages of high accuracy, non-contact, and large measurement range and is widely used in this area. We established a 3-DOF angle measurement method using two lasers and set a new algorithm to decouple its mathematical model. We analyzed the factors that may affect the resolution of this method, and achieved the simultaneous measurement of pitch, yaw, and roll angles in theory. Our method has high resolution theoretically and does not have the problem of inconsistent coordinate references.

Real-time diagnosis of the radiative properties of participatory media, such as flames, is very difficult due to their spatial and temporal complexity. In this paper, we propose a new method to simultaneously reconstruct gas and carbon soot properties using a multispectral light-field camera. Hyperspectral light-field imaging is performed on two targets (a rectangular participating medium and a flame) to analyze the spectral imaging effect of gas-solid radiative properties in the mid-infrared band. The two-color method combined with the nearest-neighbor filtering method was used to reconstruct the medium temperature and carbon soot absorption coefficients, which helps yield the gas mole fractions (H₂O and CO₂) for a specific mid-infrared band and reconstruct their actual distributions.

Fiber grating sensing technology is a widely used fiber optic sensing technology due to its ability to form a distributed sensing system for measuring multiple parameters. The number of multiplexed gratings and spatial resolution are important performance indicators of fiber Bragg grating (FBG) sensing systems. This paper proposes a fast distributed temperature measurement system based on the Optical Frequency Domain Reflectometry (OFDR) principle, using a single-mode fiber engraved with five identical weak gratings spaced 30cm apart with a reflectivity of 1% as the sensing fiber. To minimize the impact of light source nonlinearity on demodulation, we use the SiO₂ process Mach-Zehnder interferometer (MZI) module with a refractive index difference of 1.5 as an auxiliary interferometer and employ cubic spline interpolation FFT transformation for signal processing. This approach simplifies the design of the laser drive circuit and achieves a temperature resolution of 0.5°C.

In this paper, we have designed and constructed a fully digital interferometric fiber optic gyroscope (IFOG) system. The design employs photonic crystal fiber and an optical integrated chip made using thin-film lithium niobate material. The optical integrated chip contains the optical path part of the fiber optic gyroscope, which makes the light source, detector, and Y-waveguide all integrated on the chip, effectively improving the system integration. In this paper, the performance of the prototype is tested and analyzed. The test result shows that the zero-bias stability reaches 0.19°/h after running for one hour. The scale factor nonlinearity is 79 ppm in the dynamic range from -25°/s to 25°/s. The IFOG with photonic crystal fiber and an optical integrated chip containing thin-film lithium niobate Y-waveguide has been successfully miniaturized and integrated, which has the potential for commercialization and popularization.

Photoacoustic microscopy is a hybrid imaging technique that capitalizes on the photoacoustic effect to enhance imaging processes, achieving precise image reconstruction by eliminating noise within photoacoustic signals. This study introduces an innovative deep learning denoising algorithm based on score-based diffusion generative models. During the forward propagation process, the model acquires a score representation of the prior noise distribution resulting from the diffusion of the photoacoustic image. In the reverse reconstruction process, the noisy photoacoustic image serves as input. Following multiple iterations by the solver, a noise-free photoacoustic image is generated as the output. A predictor-corrector framework, trained during the forward propagation process, is employed to rectify the reverse evolution. This algorithm effectively reduces noise and demonstrates its efficacy in complex denoising challenges, thereby significantly improving the quality of photoacoustic imaging.

This study introduces Binary Fourier Perception Generative Adversarial Network (BFP-GAN), a tailored approach for improved photoacoustic image generation in data-sparse environments. By combining GAN and Fourier decay perception techniques, the method markedly enhances image quality. Experimental validation using PAM and PAT datasets demonstrates its effectiveness in reducing artifacts and improving fidelity with limited data. BFP-GAN holds significant promise for diverse clinical applications, representing a major advancement in photoacoustic imaging technology.

Limited-view photoacoustic tomography images will have a lot of artifacts and information loss when using conventional photoacoustic tomography image reconstruction algorithms. To solve this problem, this paper proposed a limited-view photoacoustic tomography reconstruction method based on a generative model. The network is trained through the noise-perturbed method and can learn a kind of scoring functions (gradients of logarithmic probability density functions) of the training dataset. The trained network has the capability to generate samples that conform to the distribution of the training dataset. Blood vessels simulation data were used to evaluate the performance of the proposed method. Experimental results on simulated blood vessels show that, compared with traditional reconstruction methods, the proposed method can effectively remove artifacts and improve image quality with measured data collected from 90°, 120°, and 180°.

The red blood cells, the role of which is difficult to underestimate in life and biology, were usually chosen as a sample for observation in an optical microscope. In this paper, we show that using optical microscopy based on high-index spherical mesoscale particles with a refractive index of 1.9, generating a non-evanescent curved light beam with subwavelength structures – so-called a structure light photonic hook by partial illumination conditions, it is possible to study the transformation dynamics of an erythrocyte into an echinocyte. Examples of images are presented. The findings in this manuscript have promising application prospects in nanomanipulation, biology, and medicine.

Photon-assisted millimeter wave system can improve real-time transmission performance of terahertz radio signals. And wireless communication is the uppermost form in nowadays communication industry. However, it is necessary to get over the multipath effect subjected to signal during wireless channel transmission. Firstly, the impact of multipath effect and the cause of frequency selective fading are introduced. Then the principle of photon-assisted mm-wave wireless transmission system is described. In this paper, we mainly focus on the frequency selective fading caused by delay extension in multipath effects, as well as the ISI and constellation distortion which the frequency selective fading generates. Here we have simulated the Rician fading channel by MATLAB, and established QPSK, 16-APSK and 16-QAM modulation techniques. Next evaluating the performance to resist frequency selective fading of these three modulation format photon-assisted mm-wave system by comparing their BER and constellation distortion. The performance has been concluded based on BER vs. MaxPathDelay and constellations output for QPSK, 16-APSK and 16-QAM over Rician channel is that QPSK is better than 16-APSK and 16-QAM. Because QPSK system over Rician channel at MaxPathDelay=9×10^-10 s, BER=0.025. When MaxPathDelay=15×10^-10, only the constellation of QPSK system does not occur significant distortion.

Weakly-coupled mode-division multiplexing (MDM) transmission technique over widely-deployed multimode fiber (MMF) is considered a promising approach to enhance the capacity of optical fiber communication systems. In order to be compatible with cost-efficient intensity-modulation/direct-detection (IM/DD) systems, effective mode-group demultiplexing approaches to simultaneously receive each mode group of MMF are highly desired. In this paper, we propose a scalable low-modal-crosstalk mode-group demultiplexer over MMF using multi-plane light conversion (MPLC), in which input Hermite-Gaussian (HG) modes of MMF are first converted to bridging modes that composed of HG₀₀ modes distributed as a right-angled triangle in Cartesian coordinates, and then each HG₀₀ mode belonging to the same mode group are respectively converted to different HG_n0 modes at the same output for simultaneous detection. With the help of bridging modes, the MPLC-based mode-group demultiplexer can scale to demultiplex more mode groups with relatively few phase masks. A 5 mode-group demultiplexer is also design for demonstration, and simulation results show that the modal-crosstalk are lower than -22.26 dB for all mode groups.

In this paper, we introduce a nonlinear phase noise suppression method for Coherent Optical Orthogonal Frequency- Division Multiplexing (CO-OFDM) systems based on Gaussian Basis Expansion (GBE). In comparison with previous phase noise suppression approaches, it enhances the system's tolerance to nonlinear phase noise evidently, effectively mitigating the nonlinear phase noise in CO-OFDM systems. The proposed method is theoretically analyzed and its efficacy is validated through simulations using VPI Software.

In this paper, we develop a Gaussian basis expansion (GBE)-based phase noise suppression method for coherent optical orthogonal frequency-division-multiplexing (CO-OFDM) systems. The GBE method displays notable advantages over conventional phase noise suppression approaches as it substantially enhances the system tolerance to laser phase noise. These theoretical benefits are further confirmed through numerical simulations conducted in CO-OFDM systems utilizing a 16-quadrature-amplitude-modulation format.

Compact air-cooling all-solid-state lasers are important in laser distance measurement, laser remote sensing detection, and scientific research. A compact 808nm LD-pumped Nd:YVO₄ laser with a compact air-cooling heat dissipation structure is designed, and the temperature field under high and low temperature operating conditions is simulated. The results indicate that the proposed structure is capable of meeting the heat dissipation requirements during the operation of the laser within an ambient temperature range of -10°C to 40°C. The temperatures of the Nd:YVO₄ crystal and the pump source are maintained at 20°C-25°C, ensuring stable operation.

This paper proposes three techniques to reduce the time required to calculate single diffraction efficiencies or a series of diffraction efficiencies obtained from rigorous coupled-wave analysis algorithms. These are a technique using the properties of the Toeplitz matrix, a technique for reducing the number of variables in a function of Fourier coefficients, and a technique for using parallel computing. On the example of tasks on plotting the dependences of the diffraction efficiency of two-layer two-relief sawtooth microstructures with antireflection coatings on the angle of incidence of radiation, it is shown that using the properties of Toeplitz matrices can significantly reduce the calculation time. Parallel computing also reduces the calculation time, but it uses more RAM.

A single-longitudinal-mode (SLM) narrow-linewidth Brillouin erbium-doped fiber laser (BEFL) is proposed and demonstrated experimentally. The erbium-doped fiber (EDF) is employed to act as both the linear gain and Brillouin gain medium, which makes it easy to excite the stimulated Brillouin scattering (SBS) in the EDF by cooperating with the ring cavity structure. In order to realize stable SLM and narrow-linewidth laser output, the fiber saturable absorber (SA) and the self-injection feedback structure are added to BEFL for the first time, which can suppress the multimode phenomenon effectively and obtain a stable SLM status. The wavelength stability is less than 1.32 pm over 45 minutes and the linewidth is as narrow as 283 Hz.

Fourier transform infrared (FTIR) spectroscopy can be used for fast, sensitive, and non-destructive quantitative analysis of gases. It is essential to extract useful information from the spectra accurately. Therefore, in this paper, a method for analyzing the FTIR spectra of gases is proposed. Savitzky-Golay convolutional smoothing is used to eliminate the noise in the spectra. A modified adaptive smoothing parameter penalized least squares method is used to eliminate baseline drift. Competitive adaptive reweighted sampling is used to select feature variables. Partial least squares regression was used to model the quantitative analysis. The infrared spectra of methane and ethane at different concentrations are obtained experimentally to verify the performance of the proposed method. The experimental results show that the proposed method can achieve smooth denoising and baseline correction of the raw spectra without losing spectral information. The screened feature variables reduce the data volume of the spectra and improve the analysis efficiency. The coefficient of determination for cross-validation (Q²) of the established quantitative analysis model was 0.99995 for the regression result of methane concentration and 0.99906 for the regression result of ethane concentration. The proposed analytical method can improve the accuracy of the FTIR spectral analysis of gases. Meanwhile, the method can also be used in other fields, such as Raman spectroscopy, laser-induced spectroscopy, and mass spectrometry.

In this paper, we present the design and simulation of a GaN-based back-illuminated ultraviolet (UV) photodetector with an absorption layer compensation doping. In the conventional UV detector, the absorption layer typically exhibits a high background doping concentration (ranging from 1.0×1015 to 1.0×1017 cm^-3), which unintentionally introduces carriers that impact the electric field distribution within the absorption layer. Consequently, the electric field near the N electrode is diminished. In the back-illumination operating mode, a substantial amount of the incident light is absorbed by the absorption layer positioned near the N electrode. This is primarily attributed to the high absorption coefficient of the AlGaN material. Consequently, the lower electric field in this region hinders the prompt conversion of the photogenerated carriers into signals. This design improves the performance of the UV photodetector by simulating the implementation of compensatory doping in the absorber layer. This helps to reduce the impact of background doping concentration. After optimization, at the peak detection wavelength of 360 nm, the compensated doped PD exhibited an unbiased peak responsivity of 0.15 A/W, as determined by spectral response simulation work.

Aiming at the requirements of optical detection and recognition for wide-area and continuous monitoring of aircraft targets, the influence of micro-scanning on the imaging and recognition performance of aircraft target is discussed in this article. This paper proposes a statistical method for aircraft target recognition threshold based on human vision. On the basis of analyzing the imaging principle of micro-scanning, the edge feature of the aircraft target is extracted using the Canny algorithm. Then the main axis direction of the aircraft target is determined based on the principal component analysis (PCA). Sampling is performed at equal intervals along the vertical direction of the main axis of the aircraft, and the characteristic parameters of the contour edge of the aircraft target are extracted. The matching algorithm of Spearman rank correlation coefficient is used to judge whether the target is recognizable. Research results show that the influence of sampling phase on target imaging can be eliminated by micro-scanning. The recognition distance of the target is significantly improved with the increase of scanning times. A smaller optical system aperture can be selected to achieve the task of target recognition when the micro-scanning imaging mode is used.

Thermal ablation is quite a complex process in high energy continuous wave (CW) laser facility, and it is crucial to understand the damage mechanism for stable operation of laser system. In this paper, we observe the behavior of contaminants-induced damage via a self-build optics testing platform. The waveband of optical coatings (Ta2O5 and SiO2) under test is dedicated for the infrared. Based on 100kW level infrared CW laser, the thermal ablation process of the optical coatings and the substrate caused by typical surface contaminants (iron micro-particle) is recorded, which shows distinct results in many aspects. This work can be helpful for understanding the influence of contaminants and prevent the optical elements from thermal damage in high energy laser system.