光波检测

近日，来自安徽科技理工大学、安徽西部大学皖西学院、复旦大学大气与海洋科学学院、上海期智研究院的联合研究团队发表了《通过实施光学条纹噪声抑制方法的激光波长调制光谱技术实现气体测量的高精度和高灵敏度检测》论文。Recently, the joint research team from Anhui University of Science and Technology, West Anhui University, Department of Atmospheric and Oceanic Sciences, Fudan University, Shanghai QiZhi Institute published an academic papers High precision and sensitivity detection of gas measurement by laser wavelength modulation spectroscopy implementing an optical fringe noise suppression method.可调谐二极管激光吸收光谱（TDLAS）已被开发用于痕量气体测量，因其高精度、高灵敏度和无需任何样品准备的原位自校准的独特优势。通常，长光程的多次通过腔体（MPC）被应用于增强基于TDLAS的传感器的检测精度和灵敏度。然而，MPC中出现的意外光学干涉纹严重影响了传感器的检测精度和灵敏度。基于MPC的TDLAS传感器的检测精度和灵敏度通常受到光学干涉纹的限制，这些干涉纹由衍射、镜面表面瑕疵的散射、镜面畸变、热膨胀、冷收缩或应力变形引起。因此，MPC中观察到的光学干涉纹由不同的光学干涉纹组成。这些光学干涉纹主要是由于少量的激光以与主激光束相差ΔL的光程到达探测器所致。这些问题对于TDLAS是普遍存在的，尤其是在使用密集重叠斑点模式的MPC时，提出了一些不同的方法来消除光学干涉纹的负面影响。The Tunable Diode Laser Absorption Spectroscopy (TDLAS) has been developed for trace gas measurement, as its unique advantages of high precision, high sensitivity and self-calibration in situ qualification with-out any sample preparation. The multi-pass cell (MPC) with a long optical path is usually applied to enhance TDLAS-based sensor’s detection precision and sensitivity. However, the unexpected optical fringes occurring in the MPC often spoil the sensor’s detection precision and sensitivity seriously. The detection precision and sensitivity of the TDLAS-based sensors containing an MPC are often limited by the optical fringes that result from diffraction, scattering on the mirror surface imperfections, mirror aberration, thermal expansion, cold contraction, or stress deformation. Therefore, the complex optical fringe consisting of different optical fringe will be observed in the MPC. These optical fringes are due largely to a small amount of laser reaching the detector with an optical path length differing by ΔL from the main laser beam. Those problems are common for TDLAS, especially using dense overlapped spot pattern MPC and some di&fflig erent methods are proposed to eliminate the negative influence of the optical fringes.研究团队提出了一种抑制可调二极管激光吸收光谱中光学条纹噪声的新方法，并将其应用于由光学条纹扰动的CH4气体传感器，以提高检测精度和灵敏度。所开发的CH4检测仪的示意图如图1所示。宁波海尔欣光电科技有限公司为此项目提供锁相放大器（HPLIA 微型双通道调制解调锁相放大器），从光电探测器输出的信号发送到锁相放大器，锁相放大器相对于同步信号对2f模式进行解调，锁相放大器的时间常数设为1ms。In this work, a novel method to suppress optical fringe noise in the tunable diode laser absorption spectroscopy is proposed and applied to the CH4 gas sensor perturbed by optical fringes for higher detection precision and sensitivity.The schematic diagram of the developed CH4 detection instrument is shown in Fig. 1 . HealthyPhoton Co.,Ltd provided a HPLIA Miniature dual-channel modulated demodulation lock-in amplifier for this project. The lock-in amplifier demodulates the signal in the 2f mode with respect to the sync signal. The time constant of the lock-in amplifier is set to 1 ms.Fig.1. Schematic diagram of the developed CH 4 detection systemlock-in amplifier (Healthy Photon, HPLIA)对于被光学条纹和随机噪声干扰的20 ppm CH4的二次谐波(2 f)信号，通过该新方法，2f信号的信噪比(SNR)从17提高到182，优化平均光谱范围Δ𝜆 。与未经处理的原始信号相比，CH4测量精度改善了约1.5倍。相应的最小可检测浓度可从3 ppb改善到0.78 ppb。系统的相应噪声当量吸收灵敏度(NNEA)和噪声当量浓度(NEC)分别为6.13 ×10-11 cm&minus 1 W Hz&minus 1/2 and 0.181 ppm。For the 2nd harmonic(2f) signal of 20 ppm CH4 spoiled by optical fringes and random noise, by the novel method, the signal-to-noise ratio (SNR) of the 2f signal is improved about 6.5 times from 17 to 182 with an optimal averaging spectral range Δ𝜆 . A &sim 1.5 times improvement in the measurement precision of CH4 is achieved compared to unprocessed raw signal. The corresponding minimum detectable concentration can be improved from 3 ppb down to 0.78 ppb. The corresponding noise equivalent absorption sensitivity (NNEA) and the noise equivalent concentration (NEC) of the system is 6.13 ×10-11cmW-1Hz-1/2 and 0.181 ppm, respectively.Violet line from traditional averaging method and magenta line from the novel optical fringe noisesuppression method.Histogram plot of the 20 ppm CH 4 deviation.20 ppm CH 4 Allan-deviation stability of developed overlapped spot pattern MPC.参考文献：Reference:Yanan Cao, Xin Cheng, Zong Xu, Xing Tian, Gang Cheng, Feiyan Peng, Jingjing WangHigh precision and sensitivity detection of gas measurement by laser wavelengthmodulation spectroscopy implementing an optical fringe noise suppression method, Optics and Lasers in Engineering 166 (2023) 107570www.elsevier.com/locate/optlaseng

关于发布国家生态环境标准《短波广播发射台电磁辐射环境监测方法》的公告 为贯彻《中华人民共和国环境保护法》，保护环境，防治电磁辐射环境污染，规范短波广播发射台电磁辐射环境监测工作，现批准《短波广播发射台电磁辐射环境监测方法》为国家生态环境标准，并予发布。　　　　标准名称、编号如下。　　　　《短波广播发射台电磁辐射环境监测方法》（HJ 1199-2021）　　　　本标准自2022年1月1日起实施。短波广播发射台电磁辐射环境监测方法.pdf.pdf生态环境部　　2021年10月29日　　　　生态环境部办公厅2021年11月1日印发

激光波形探测器/激光波形探测仪型号：BGS-141 BGS-141 型激光波形探测器是针对脉冲激光波形测试而设计的。使用该探测器接收激光,结合速示波器可以准确测量激光脉冲的波形、脉冲宽度。再配合激光能量计测量激光的输出能量可以获得峰值率等参数。探测器选用了速的PIN光电管,具有很好的稳定性。仪器作采用9V电池供电,使仪器轻巧便携。光谱范围有400 ~ 1100nm 或者800 ~ 1600 nm 两种, 用户根据被测激光波长选择其中种响应时间1ns响应度0.8mA/mW (1.3mm处)电源DC 9V 积层电池作环境0 ~ 40 ℃, 相对湿度≤ 80 %