Achieving precise spatiotemporal synchronization between laser pulses and tin droplets is essential for generating stable, high-conversion-efficiency radiation in laser-produced plasma extreme ultraviolet light sources. This requires accurate position measurements of tin droplets to trigger laser pulses. Given the droplets' small size, high velocity, high repetition rates, and strong background noise in extreme ultraviolet (EUV) systems, droplet positioning demands exceptional accuracy, speed, and noise immunity. To address this challenge, we propose a droplet spatial positioning measurement technology (DSPMT) featuring a two-dimensional subpixel localization method based on Fourier-based frequency phase shift (FBFPS). The method features high positioning accuracy, real-time performance, and noise resistance. Simulation results demonstrate its superiority over conventional subpixel localization methods in both precision and speed, with enhanced noise robustness. In droplet-triggered laser shooting experiments, the localization error remained below 1.1 mu m, whereas the processing time was within 10 mu s per frame. Compared with conventional methods, the computation speed increased by 33.12%, and the positioning accuracy improved by 35.86%. Following the implementation of the FBFPS method, the DSPMT not only achieves high-speed and high-accuracy droplet localization but also facilitates two critical functionalities in the spatiotemporal synchronization shooting system of EUV light sources, including droplet velocity measurement and shooting accuracy evaluation.

Yam is a kind of traditional Chinese medicine which contains many substances. It is of great significance to ensure the safe use of yam. In this article, the Raman peaks of the three pesticides, i. e., fenthion, triazophos, and thiram, were calculated by Gaussview/Gaussian09w. By combining with the surface-enhanced Raman spectroscopy (SERS) of the standard pesticide solutions, the Raman characteristic peaks of these three pesticides are determined. The pesticide residues of fenthion, triazophos, and thiram in yam were studied by using the selfassembled confocal Raman microscope as the detection device, and the gold nanosol was used as the enhanced substrate of SERS. The volume ratio of pesticides, hydrochloric acid, and gold sol particles was optimized experimentally. The experimental results show that the Raman peak bands of fenthion pesticide are around 717, 1050, and 1221 cm(-1), the lowest detection limit is 1 mg . L-1, and the linearity R between the intensity of Raman peak and fenthion pesticide concentration is 0. 9762 within the fenthion concentration range of 5. 15 mg . L-1. The Raman peak bands of triazophos are around 611, 978, 1001, 1321, 1408, and 1597 cm(-1), the minimum detection limit is 1 mg.L-1, and the linearity is 0. 9087 within the concentration range of 5. 9 mg.L-1. The Raman peak bands of thiram are around 556, 865, 1146, and 1506 cm(-1), the minimum detection limit is 0. 1 mg.L-1, and the linearity is 0. 9905 within the concentration of 0. 20 mg.L-1. It is expected that the rapid on-site detection of pesticide residues in traditional Chinese medicines can be realized by using gold as the enhanced substrate for SERS.

在传统的喇曼光谱检测过程中,喇曼光谱的有效信号有时会被荧光背景淹没,难以识别.为了准确、有效地分离差分信号和基线偏差,将差分喇曼技术和误差反向传播神经网络算法相结合,提出了差分喇曼解调和去噪算法,并进行了理论和实验验证.对市售的百草枯、补肾丸、机油以及海洛因等荧光较强的物质进行了检测分析.结果表明,可以得到有效的物质喇曼特征谱图.很好地解决了目前行业应用中检测的难题.

Library-based matching recognition is the key to the application of Raman spectroscopy for material composition identification, which directly affects the accuracy of matching results. For the library matching, especially for the mixture spectrum, the single matching feature can not fully reflect the similarity between the measured sample spectrum and the spectral spectrum in the library. The spectral matching needs to comprehensively consider multiple matching features. In this paper, a new spectral integration matching method is proposed by using the logistic regression mathematical model to fuse the peak matching coefficient, the non-negative least squares matching coefficient and the cosine matching coefficient. The new method takes into account both the spectral peak information and full spectrum information of the sample. The experiment results based on the Raman spectroscopy library matching of 20 kinds of amino acid mixtures show that the spectral integration matching method has lower false positive rate.

In recent years, portable spectrometer technology has developed rapidly. Compared with the traditional spectrometer, CCD spectrometer in the spectral collection of the way there have been two changes : (1) The signal is superposed and integrated to generate the spectrum, and the traditional SNR estimation method cannot obtain the detector fluctuation by a single detection. (2) For the spectral noise, the detector responses to random fluctuations and scanning repetitive errors are transformed into differences in pixel response of the CCD detector, detector random noise and mode noise related to the resolution of the optical system. Therefore, it is of great practical significance to propose a more adaptive spectral quality assessment method based on the measured spectrum. According to the changes of Raman spectrometer detector, we analyze the components of the collected spectral signal, and put forward the noise model assumptions of CCD spectrometer on the basis of the analysis. According to this assumption, different signal extremum frequencies are used to separate different noise pixels and the noise frequency mode is numerically simulated. The simulation results are consistent with the assumptions. On the basis of this, we propose and experimentally validate the method for evaluating SNR of Raman spectroscopy to estimate spectral line noise through spectral line spacing. The method includes the following two steps : (1) Collecting multiple measured spectra for superposition, counting the number of spectral extreme points corresponding to different frequencies in the superposition process, and obtaining the statistical results to separate the environmental noise and dark noise in the spectrometer; (2)Applying the above separation results, the statistical average of the spectral line extreme points corresponding to the dark noise in the measured spectrum is calculated, and then the SNR is calculated according to the formula in the text. After the preliminary preparation of step (1), the method can evaluate the random noise of the CCD Raman spectrometer through a single spectrum and evaluate the spectral SNR. In this paper, three Raman spectroscopy systems with the same optical structure and different CCD detectors are used to experiment. By using this method, the spectral quality is controlled by setting the SNR threshold, and a uniform spectral curve is obtained. Based on the method proposed in this paper, the SNR is fitted to the synchronization overlapping average algorithm, and the goodness of fit is up to 98%. The method can be used to evaluate the performance of Raman spectrometer and acquire real-time quality control of Raman spectrum. Theoretical and experimental results show that for the CCD detector-based Raman spectrometer, the SNR can be obtained based on this method when determining the sample and the characteristic peak. The method can also be used to compare different configurations of Raman spectroscopy equipment and as a standard to control the quality of spectra.

Peak detection is an important step in the chemical identification by Raman spectroscopy. At present, most peak detection methods have finite identification ability on overlapping peaks, especially for the spectrum measured by the portable spectrometer with low resolution. In this paper, an improved method is proposed that using continuous wavelet transform(CWT) peak detection method based on a new wavelet on the deconvolved Raman spectrum. The new wavelet has smaller linewidth and is more similar with the intrinsic line profile of Raman spectroscopy, Lorentz line profile. So it has advantages on overlapping peaks detection. The proposed method was evaluated by Raman spectrum of solid amino acid mixtures. The results show that it is better at detecting overlapping peaks than the other two wavelets.

Peak detection is a particularly important pre-processing step in chemical identification using Raman spectra. At present, most peak detection methods have limited applicability when there are overlapping peaks, especially the spectrum measured by portable spectrometers with low resolution. In this paper, an improved method is proposed based on the application of continuous wavelet transform (CWT) peak detection using a new wavelet to the deconvolved Raman spectrum. The new wavelet has a smaller linewidth and is more similar to the intrinsic Lorentz line profile of the Raman spectrum. It, therefore, has several advantages with regard to the detection of overlapping peaks. The proposed method was evaluated using the Raman spectrum of solid amino acid mixtures, and the results show that it is better at detecting overlapping peaks than the two other investigated wavelets. The receiver operating characteristic curves show that this method can detect more true peaks while maintaining a low false discovery rate. Moreover, the maximum of the true positive rate is the largest in the new approach, which indicates better performance for overlapping peak detection.

Atomic clocks based on laser-cooled atoms are widely used as primary frequency standards. Deploying such cold atom clocks (CACs) in space is foreseen to have many applications. Here we present tests of a CAC operating in space. In orbital microgravity, the atoms are cooled, trapped, launched, and finally detected after being interrogated by a microwave field using the Ramsey method. Perturbing influences from the orbital environment on the atoms such as varying magnetic fields and the passage of the spacecraft through Earth’s radiation belt are also controlled and mitigated. With appropriate parameters settings, closed-loop locking of the CAC is realized in orbit and an estimated short-term frequency stability close to 3.0 × 10 −13 τ −1/2 has been attained. The demonstration of the long-term operation of cold atom clock in orbit opens possibility on the applications of space-based cold atom sensors.

Aimed at eliminating the fluorescence interference from containers of the sample in the detection of Raman spectroscopy, a dual-axis confocal detection scheme is proposed based on the characteristic that the fluorescence generated by the container and the Raman signal of the sample arc not confocal. The experimental results show that the fluorescence interference signals from the container arc reduced by an order of magnitude, and the intensity of Raman signal decreases by about 30%. The dual-axis confocal Raman detection scheme can solve the mixed reception problem of Raman signal and fluorescence in the conventional coaxial confocal Raman detection scheme, solve the limitation of the dynamic detection range of Raman signal caused by the fluorescence interference, and achieve the effective detection of Raman signal of the material in fluorescent material containers.

A new discrimination algorithm of Raman spectral peaks is proposed. With Voigt function as the fitting function, the spectral peaks obtained after the ridge peak detection based on the wavelet transformation are fitted. The similarity of spectral peaks before and after fitting is taken as the basis for discrimination of spectral peaks. The Raman signal with amplitude comparable to that of noise is effectively discriminated. Compared with those of the existing two discrimination methods of spectral peaks, the true positive rate of the proposed method improves by 60％ when the false data rate is 5％ and the false data rate of the proposed method decreases by 10％ when the true positive rate is higher than 90％.

Since the atomic clock was invented, its performance has been improved for one digit every decade until 90s of last century when the traditional atomic clock almost reached its limit. With laser cooled atoms, the performance can be further improved, and nowadays the cold atom based clocks are widely used as primary frequency standards. Such a kind of cold atom clocks has great applications in space. This paper presents the design and tests of a cold atom clock (CAC) operating in space. In microgravity, the atoms are cooled, trapped, launched and finally detected after being interrogated by microwave field with Ramsey method. The results of laser cooling of atoms in microgravity in orbit are presented and compared with that on ground for the first time. That the full width at half maximum (FWHM) of obtained central Ramsey fringes varies linearly with launching velocity of cold atoms shows the effects of microgravity. With appropriate parameters, a closed-loop locking of the CAC is realized in orbit and the estimated short term frequency stability of 3.0× 10 ^-13/√(τ) has been reached.

We describe a highly reliable optical system designed for a rubidium space cold atom clock (SCAC), presenting its design, key technologies, and optical components. All of the optical and electronic components are integrated onto an optimized two-sided 300  mm×290  mm×30  mm optical bench. The compact optical structure and special thermal design ensure that the optical system can pass all of the space environmental qualification tests including both thermal vacuum and mechanical tests. To verify its performance, the optical system is carefully checked before and after each test. The results indicate that this optical system is suitably robust for the space applications for which the rubidium SCAC was built.

针对氨气(NH3)和二氧化硫(SO2)气体吸收谱线在196～214 nm波段区域存在谱线重叠的问题,在采用傅里叶变换的差分吸收光谱法测量气体浓度基础上,采用分波段方法,解决NH3和SO2特征频谱相互串扰对测量的影响,采用非线性修正方法,解决在SO2高浓度情况下出现的非线性吸收对NH3气体测量的影响,采用经验模态分解(EMD)降噪处理方法,提高信噪比,最终实现对NH3和SO2气体浓度的同时准确测量.实验结果显示,NH3各个浓度测量误差均在±0.15mL/m3以内,相对误差不超过±1.5％,最低可探测浓度为1.5 mL/m3;SO2各个浓度测量误差均在±2 mL/m3以内,相对误差不超过±1％,最低可探测浓度为16 mL/m3.

The frequency of a distributed feedback diode laser (DFB-LD) is stabilized on Cesium ((133)Cs) D(2) saturated absorption lines by the polarization rotated optical feedback method (PROF). Different from the conventional frequency stabilization methods by adjusting the LD pump current, no extra electrical feedback is needed with the PROF. The self-homodyne beat spectra FWHM linewidth of the DFB laser is measured to be 1.1 MHz, greatly reduced by a factor of about 40 from its free-running linewidth of 44 MHz; and the optical frequency drift is reduced from 96 MHz down to 6.6 MHz.

研制了一套基于数字反馈稳频的便携式瓦斯浓度遥测装置,采用电流和温度双重反馈稳频的策略抑制了激光器波长的长期漂移,同时也保证了光功率的长期稳定性。实验结果表明,9h内激光器波长的长期漂移小于1.2pm,光功率保持稳定,保证了瓦斯浓度的长期连续稳定的测量;不同距离下浓度测量值重复性较好,浓度波动小于5%,满足实际环境中（如天然气管道泄漏、煤矿等）瓦斯浓度测量需求。

针对多普勒测风激光雷达系统的应用需求,研制了一套结构紧凑、操作灵活的Pound-Drever-Hall（PDH）激光稳频系统。直接数字频率合成器（DDS）产生激光器高频相位调制信号,模拟混频器解调激光器的频率漂移信息,高集成度的数字信号处理器（DSP）作为稳频控制系统的心脏,负责整个稳频系统的总线控制、信号处理及比例积分微分（PID）伺服等。实验表明,在2.5h内激光器的相对频率漂移不超过±17kHz,其均方根（RMS）误差为5kHz,绝对频率稳定度优于200kHz。在主动对法布里-珀罗干涉仪（FPI）施加6 Hz固定扰动时,系统能够在30ms内迅速恢复稳定。满足直接探测多普勒测风雷达系统中0.1m/s测风精度的应用需求。

This article introduces the design of the software and hardware of the portable ship liquid cargo tank capacity inquiry system. Acquiring the height of liquid surface,the parameters of trim,density and temperature,the interface of the system displays the weight and volume of liquid in tank. As the result of storing the parameters and computing results,the system reduces the workload of querying tables and computing of metrology personnel. The system improves work efficiency and ensures that the measurement results are accurate and reliable in order to provide convenience for digital management and inspection.

We demonstrate a tunable wavelength-locked seed laser source with high-frequency stability to realize the precise measurements of global atmospheric wind field. An Nd:YAG laser at 1 064 nm is used as the master laser (ML). Its frequency is locked to a confocal Fabry-Perot interferometer by using the Pound-Drever-Hall method, which ensures the peak-to-peak value of its frequency drifts less than 180 kHz over 2 h. Another Nd:YAG laser at 1 064 nm, as the slave laser, is offset-locked to the above ML using optical phase locked loop, retaining virtually the same absolute frequency stability as the ML. The tunable ranges of the frequency differences between two lasers are up to 3 GHz, and the tuning step length was an arbitrary integral multiple of 200 kHz. The researched seed laser source is compact and robust, which can well satisfy the requirement of the Doppler wind lidar.

A novel beam-steering external cavity diode laser using an intracavity lead lanthanum zirconate titanate (PLZT) electro-optic ceramic deflector is proposed and demonstrated experimentally. The laser consists of a semiconductor laser with single mode fiber coupled output, polarization controller, PLZT electro-optic ceramic deflector, and output concave mirror. By applying proper driven electrical signals on the PLZT electro-optic deflector, the beam deflection angle achieves 5.8 mrad at 1 000 V. A high-speed beam-steering property with less than 120-ns switching time is also observed. Moreover, a good beam quality with Gaussian spatial profile and a linear polarization state are obtained.

为检验扫描镜的动态性能,提出了一种动态自准直检测方法,该方法巧妙地将被检扫描镜和动态靶标上目标模拟反射镜纳入动态光电自准直仪准直光束的传播路径中,并构成闭合的光学自准直测量回路。设计了扫描镜动态性能的自准直检测装置,并利用自准直方法对动态靶标的自身精度进行标定。实验结果表明,动态靶标在360°的范围内的动态精度为±15μrad,可检测最大速度为80°/s,最大加速度为50°/s2。将该检测方法和装置应用于某型号空间激光照明成像跟踪系统中扫描镜的方位轴、俯仰轴独立性能的检验,获得了相应的静态轴系晃动、阶跃响应和连续跟踪等性能数据,为扫描镜的性能改进提供了参考和帮助。