Formaldehyde (H2CO) is a hazardous volatile organic compound widely present in indoor and industrial environments, and its real-time, highly sensitive detection is essential for environmental safety. However, existing detection techniques often face challenges in simultaneously achieving high sensitivity and long-term stability, and many conventional photoacoustic spectroscopy (PAS) systems rely strongly on low gas flow rates to suppress flow-induced noise, which limits their applicability for continuous online monitoring. In this work, an ultraviolet photoacoustic spectroscopy (UV-PAS)-based H2CO detection system operating in a nitrogen (N2) background is developed. The system integrates a compact differential photoacoustic cell (PAC) with a 320 nm ultraviolet laser source, in which the resonator length and buffer configuration are carefully optimized to enhance acoustic resonance and effectively suppress flow-related disturbances. Notably, a key innovation of this study is that the system maintains a stable photoacoustic response even under relatively high gas flow conditions. Experimental results demonstrate that at a flow rate of 250 sccm, the photoacoustic signal amplitude remains stable, and the noise level is well controlled, significantly reducing the dependence of conventional PAS systems on low-flow operation. The photoacoustic cell exhibits a resonant frequency of 1767 Hz and a quality factor of 46. Calibration using a 47.31 ppm H2CO:N2 gas mixture shows a good linear response with a correlation coefficient of R2 = 0.98844. The minimum detection limit reaches 2.50 ppm at a 1 s integration time and is further improved to 88.1 ppb at an integration time of 2202 s based on Allan-Werle deviation analysis. These results demonstrate that the proposed UV-PAS system provides a sensitive, stable, and cost-effective solution for real-time trace H2CO detection while retaining robust performance at elevated gas flow rates, highlighting its strong potential for practical applications.

To address the growing demand for Terahertz Time-domain Spectroscopy (THz-TDS) in remote sensing and applications requiring standoff detection, this work presents the comprehensive design and validation of a robust, all-polarization-maintaining (all-PM) erbium-doped femtosecond fiber laser system. The primary technical challenge addressed is the significant degradation of ultrashort laser pulses during transmission over optical fibers exceeding 10 meters. This degradation, driven by a complex interplay of Group Velocity Dispersion (GVD) , higher-order dispersion effects, and Self-Phase Modulation (SPM), leads to severe pulse broadening and soliton fission, critically limiting the operational range and signal-to-noise ratio in harsh or remote environments. To overcome these limitations, a methodical approach combining detailed numerical modeling and rigorous experimental implementation was adopted. A sophisticated propagation model was developed using the split-step Fourier method to solve the Generalized Nonlinear Schr & ouml;dinger Equation, accurately simulating the pulse dynamics by incorporating gain, loss, and higher-order nonlinear effects. By leveraging the high birefringence of PM fibers to constrain pulse propagation to a single principal axis, the model effectively optimized a dynamic dispersion compensation scheme. A key theoretical innovation was the use of an asymmetric loss strategy to independently control the soliton order (N) in the pump and probe arms, ensuring both remained below the critical fission threshold (N < 3) to prevent pulse breakup and maintain temporal integrity. Based on the optimized parameters derived from the simulation, a 100 MHz repetition-rate lasersystem was experimentally constructed. The system features a multi-stage amplification architecture and is built entirely with PM components connected via precision fusion splicing. This all-PM design intrinsically suppresses phase noise and provides superior immunity to environmental disturbances such as temperature fluctuations and mechanical vibrations, which would otherwise induce polarization mode dispersion and degrade signal quality. The experimental results demonstrate exceptional performance and validate the theoretical model. After transmission through an 11.29-meter pump path, the system delivered high-quality pulses with a duration of 89.0 fs and an average power of 42.56 mW. Concurrently, the 11.15-meter probe path produced 88.0 fs pulses at an average power of 30.46 mW. Both output channels exhibited a broad spectral bandwidth exceeding 90 nm at the 3 dB level, which is ideal for efficient THz generation. Furthermore, the system's stability was confirmed through a continuous 12-hour operational test, which recorded power fluctuations of less than 0.5% RMS, underscoring its robustness and reliability for practical deployment. In conclusion, this research successfully demonstrates the high-fidelity transmission of sub-100-femtosecond pulses over a 10-meter fiber optic link. The synergistic approach of combining dynamic dispersion management with a fully polarization-maintaining architecture provides a stable, highperformance source for THz-TDS. This work represents a significant advancement in the practicalization of fiber-coupled THz-TDS systems, paving the way for their reliable deployment in demanding real-world scenarios such as standoff explosive detection and industrial process monitoring.

Mid-infrared frequency-comb spectroscopy enables measurement of molecules at megahertz spectral resolution, sub-hertz frequency accuracy, and microsecond acquisition speed. However, the widespread adoption of this technique has been hindered by the complexity and alignment sensitivity of mid-infrared frequency-comb sources. Leveraging the underexplored mid-infrared window of silica fibers presents a promising approach to address these challenges. In this study, we present the first, to the best of our knowledge, experimental demonstration and quantitative numerical description of mid-infrared frequency-comb generation in silica fibers. Our all-silica-fiber frequency comb spans over two octaves (0.8 μm to 3.4 μm) with a power output of 100 mW in the mid-infrared region. The amplified quantum noise is suppressed using four-cycle (25 fs) driving pulses, with the carrier-envelope offset frequency exhibiting a signal-to-noise ratio of 40 dB and a free-running bandwidth of 90 kHz. Our developed model provides quantitative guidelines for mid-infrared frequency-comb generation in silica fibers, enabling all-fiber frequency-comb spectroscopy in diverse fields such as organic synthesis, pharmacokinetics processes, and environmental monitoring.

光谱范围和信噪比是评价太赫兹时域光谱仪性能的重要参数.为了解决太赫兹时域光谱仪光谱范围和信噪比的校准问题,介绍了太赫兹时域光谱仪的构成及原理,比较了目前常用的光谱范围和时域信噪比校准方法的优缺点,并优选其中一种方法,设计了太赫兹时域频域信噪比参数校准方法.以空测时频域信号幅值最大值的 1/M对应的频率范围作为光谱范围,研究了M取值对光谱范围的影响.M值越大,则光谱范围越宽.当M值≥50时,光谱范围变化不大.对空测时域信号的信号和噪声进行定义,并计算出时域信噪比.以空测时的频域功率谱作为信号,以金属板遮挡光路时的频域功率谱作为噪声,从而计算出频域信噪比.进行了光谱范围和信噪比校准实验,采用对照法研究了湿度变化对太赫兹时域光谱仪测量范围和信噪比参数的影响.当相对湿度≤50%时,对光谱范围和时域信噪比影响不大;当相对湿度＞50%时,因为空气中水蒸气对于太赫兹的吸收急剧增加,光谱范围和信噪比急剧缩小.

Fizeau wavelength measurement plays an important role in the fields of laser technology, optical communication, and optical metrology. The accuracy of the traditional multistage Fizeau wavemeter is limited owing to the degradation of the stripe symmetry and finesse caused by variations in the cavity length. Herein, we propose a virtual Fizeau cavity (VFC) based on the principle of phase difference to address this issue. The principle analysis and simulation of this measurement system are presented, along with experiments that verified the feasibility and performance of the VFC method. The wavelength measurement accuracy of this system is superior to 60 MHz in the 350-1100 nm wavelength range. The design concept of "virtual-real combined" cavities first proposed in this paper to our knowledge introduces possibilities for the development of high-accuracy Fizeau wavelength measurements.

为了满足高分辨率光谱仪高灵敏度、高分辨率、低噪声的技术要求,设计了用于微光成像系统的背照式CCD驱动电路及主控电路.线阵CCD采集系统采用Altera公司的MAX X系列FPGA作为核心控制器件,为线阵CCD提供多路驱动信号;线阵CCD探测器输出模拟信号经过信号预处理及AD采样,变换为数字信号后通过USB接口模块发送给光谱仪.通过将线阵CCD采集系统安装到高分辨率光谱仪,对汞灯谱线进行特征峰测试,光谱分辨率可以达到0.062 nm,满足高分辨率光谱仪的探测要求.

微光夜视仪是信息化战争夜战中必备的一种仪器，广泛应用于夜视单兵侦察、枪瞄、车载、机载等作战领域。分辨力是衡量微光夜视仪探测能力的重要参数，是反映其综合性能的关键指标之一。为了解决现场使用、保养和维修等全寿命周期的各个环节中微光夜视仪的性能保障难题，研制了便携式微光夜视仪分辨力测试系统，主要组成部分包括光源组件、供电电池、靶标转轮、成像物镜、照度计、电池电压测量反馈模块、适配器和触摸显示屏等，实现了对微光夜视仪分辨力的测试，可在现场替代实验室测试系统，弥补其体积大、不便携带等缺陷。

针对fJ(飞焦)至单光子极弱能量测量及溯源需求,提出一种纠缠单光子源.通过基于冷原子团的自发四波混频效应产生波长795 nm的宣布式纠缠光子对,采用背景辐射抑制与实时补偿、高精度激光稳频、时序脉冲精密同步获得窄线宽、高质量的单光子源.在此基础上,研究了纠缠光子源参数校准方法,进一步建立以量子基准为基础的全新光辐射量值溯源体系,减小了极弱光辐射参数的测量不确定度.

发散角是太赫兹源光束特性的重要衡量指标,是太赫兹光学系统设计的重要参数.研究了太赫兹源发散角测量原理,设计了一种由精密弧形导轨、斩波器、狭缝组件、太赫兹高莱探测器、锁相放大器和计算机系统组成的测量装置,设计了一种由自准直仪、光学角规和CCD相机组成的发散角测量装置标定模块,对太赫兹肖特基倍频源和太赫兹雪崩固态源的发散角进行了测量.此外,对测量结果不确定度进行了评定,其不确定度水平达到Urel=3.2%(k=2).太赫兹源发散角的准确测量为深空探测、战术通信、反隐身、战场隐蔽目标识别等领域提供了有力的支撑.

In order to evaluate the integrated properties of visible photoelectric imaging system exactly and objectively ,the calibration equipment was developed .The equipment was com‐posed of integrating sphere ,standard card ,off‐axis reflective collimator ,mechanical adjust‐ment bench ,video acquisition module and comprehensive software .It could complete a meas‐urement of resolution ,contrast ,optical transfer function(MTF) ,noise power spectrum ,noise equivalent light and sensitivity .For a certain visible photoelectric imaging product ,the effec‐tiveness of the equipment was proved .The comprehensive parameter measurements are given :the cut‐off frequency is 39 .4 mm-1 , the contrast is 76 .5% ,the root‐mean‐square (RMS ) noise is 2 .14 mV ,the noise equivalent light (NEL ) is 0 .045 5 cd/m2 and the sensitivity is 47 mV · (cd/m2 )-1 . In addition ,an illuminometer and a standard video pattern generator were respectively adopted for making calibration , results show that the maximum relative measurement errors of integrating sphere and the signal acquisition system are -2 .3% and 1% .

The invention discloses an infrared radiometer proportional constant calibration method on the basis of a standard plane source black body and belongs to the field of infrared optimal radiation. The calibration method aims at the characteristics that a chopper of a current infrared radiometer is sprayed with high-emissivity black paint and the current infrared radiometer is provided with four temperature probes; when the temperature of the chopper is equal to that of a built-in temperature control reference black body, a signal is acquired, so that additional radiation of the chopper is avoided entering a detector; and moreover, in the signal acquiring process, the environment temperature, the temperature in a shell and the temperature of the chopper are requested to be equal to enable radiation among the environment, the shell and the chopper is dynamically balanced, and thus, influence of additional radiation of the chopper, the inside of the shell, the environment and the like can be eliminated. In addition, in the calibration method, calibration of a plurality of temperature points is also carried out in a common environment temperature range, so that the defect of replacing a plane with points in a conventional method, i.e. one temperature point replaces a plurality of temperature points to carry out calibration, is overcome. Compared with the prior art, the infrared radiometer proportional constant calibration method has higher accuracy.

The spatial noise on staring array thermal imager restricts its capability in detecting , distinguishing and tracking the long distance targets .To solve the problem in measuring the thermal imager spatial noise ,its measuring theory was analyzed and the mathematical model for measuring the spatial noise based on signal transfer function (SiTF) was presented .After removing the temporal noise equivalent temperature difference (NETD) from the noise of a certain group or district or the whole pixels in thermal imager ,the spatial NETD model was calculated through analyzing statistically the noise of those pixels .In measuring the SiT F and spatial NETD of cooled MCT320 × 256 thermal imager ,when the temperature of the back‐ground blackbody is 5 ℃ ,the SiTF of central district in field of view(FOV) is 27 .29 mV/℃ , and the spatial NETD is 0 .128 ℃ .When the temperature of the background blackbody is 20 ℃ ,the SiTF of central district in FOV is 29 .03 mV/℃ ,and the spatial NETD is 0 .121 ℃ .The measuring results show that the measuring method can evaluate the influence of spatial noise on the perform‐ance of thermal imager .

The image plane illumination nonuniformity caused by optical system or detector will affect the detection precision of photoelectric imaging system, especially in image guidance, positioning and recognition. An image plane illumination uniformity measurement device was set up, which was characteristiced of high uniformity and wide dynamic range. The device was composed of an asymmetric integrating sphere，the image collection and processing system, as well as the electrical control system.The asymmetric integrating sphere had two different radius,which was respectively 800mm and 1000mm.The spectral region was （0.4~1.1）μm, the illumination range was (1×10-4~2×104)lx. The image collection and processing system had two different acquisition card,which were respectively used for analog and digital signals. The software can process for dynamic image or static image. The TracePro software was used to make a internal ray tracing of integrating sphere, the illumination uniformity at the export was simulated for the size of 330mm×230mm and Φ 100mm export, the results were respectively 97.95% and 98.33%. Then,an illuminometer was used to measure the actual illumination uniformity of integrating sphere, the result was shown the actual illumination uniformity was 98.8%. Finally, a visible photoelectric imaging system was tested ,and three different uniformity indicators results were given.

The imaging plane's illumination nonuniformity is an important parameter for wide FOV and short-focus optical imaging system. But now the imaging plane's illumination nonuniformity measurement device can not meet the requirements of wide FOV, high uniformity and wide dynamic range. A new device combined with assymmetric double-hemisphere technology was set up. It was composed of the special integrating sphere, CCD camera, precision displacement mechanism, image acquisition, and testing software. The CCD was pre-calibrated and the testing software realized a auto-correction, image acquisition, display and the illumination nonuniformity calulation. The light source was calibrated by the national standard color temperature lamp. The device can provide a Lambert object surface. The advantages of the device were that the FOV was as largely as 100, and a wide illumination range of (10-3 similar to 103)Lx was achieved. An optimal simulation of assymmetric double-hemisphere was calculated by LightTools,it was proved that the illuminace nonuniformity at the outlet was better than 1.7%.Finally, the illumination nonuniformity of the integrating sphere and a wide FOV and short-focus lens were respectively measured. The results show that, the illumination uniformity of the integrating sphere is less than or equal to 1.49%,and the imaging plane's illumination nonuniformity of the lens is 10.24%.

When the carrier aircrafts land on the ship,carrier optical landing aid system is required on occasion.The lamp simulator used halogen tungsten light as light source,and a light uniformizer was added beside the light source.Then the beam shaping conical cavity was added according to the distribution of outgoing beam of light source.According to the demand of field angle,a cylinder array optical system was added at a certain distance.Then optical filter and optical attenuator were added at the exit pupil of the simulator.The lamp simulator had red,yellow,green spectrum,the horizontal field angle was 30 degree,the vertical field angle was 20 degree,the light intensity was over 10 000 cd,the uniformity of the lamp-house was better than 8%,and the light intensity was adjustable.

According to the definition of relative distortion,a distortion measurement with inverse imaging method was proposed.We first placed the target on the focus surface of the unit-under-test(UUT),put the entrance pupil position of the UUT at the rotation axis position of the precise turntable,and rotated the UUT from the forward maximum field of view(FOV) to the negative maximum FOV,then measured 14 FOV points and finally obtained the distortion value of each FOV.Distortion value of the whole FOV could not be measured unless the entrance pupil position of the UUT was put at the rotation axis position of precise turntable strictly.The accuracy of focal length measurement is 2 μm,and the accuracy of relative distortion measurement is 0.5‰.

In order to solve the calibration of the infrared imager test equipment,a kind of infrared radiometer in which the temperature of interior reference blackbody was equal to the environmental temperature was designed.In order to evaluate this kind of radiometer and give guidance to the infrared radiometer design,a mathematic model for infrared radiometer noise equivalent temperature difference(NETD)was given.The NETD of infrared radiometer was estimated under different electronic bandwidths and spectral wavebands.The results show that when noise equivalent bandwidth is within 1 Hz,NETD of infrared radiometer in mid-wavelength infrared(MWIR) and long wavelength infrared(LWIR) spectral bands is smaller than 0.01℃,which can meet the requirements of the calibration of infrared imager test equipment.

Based on the corresponding relation of the fourth coefficient q 4 from the Zernike polynomial and the focus item from the Seidel aberration, the value of the fourth coefficient q 4 from the Zernike polynomial is used as the criterion of the focusing method for laser interferometer. The focusing method using the criterion is feasible and the result of focusing method is steady. Besides, the positive or negative of the q 4 can be used to judge whether the piont of intersection of the spherical wave from the interferometer is in front of the focus plane or behind the focus plane of a large aperture off-axis parabolic collimator, which will guide the move direction. The focus plane of the large aperture off-axis parabolic collimator is confirmed by using this method. From the calibration experiment, It's known that the focusing effect is perfect and the parallelism error of emissive beam from collimator is less than 0.22″.

Several bore-sight methods for multi-spectral optical axes used nowadays were compared.Based on a large aperture collimator,a new bore-sight method for optical axes parallelism was put forward by using CCD technology.In this method,the ZYGO interferometer was used for accurately focusing.By comparing the center coordinates of the conjugated image on CCD of the target with the center coordinates of the laser spot of the system under test,the parallelism between the visible axis or infrared axis and the laser axis was calculated.The focal plane of large aperture off-axis paraboloid was determined and analyzed,and the center position of the laser spot was determined as well.The measurement uncertainty was analyzed and the uncertainty of 5″ was obtained.