A fiber micro-vibration sensor based on single-mode fiber ring laser

A new micro-vibration sensor based on single-mode fiber ring laser is put forward. The Mach-Zehnder interferometric （MZI） detection technique is presented for interrogating laser frequency shift due to the measurand （piezoelectric transducer （PZT） is used to simulate the micro-vibration） induced laser cavity strain from both single- and multi-mode lasers. In the experiment, compared with multi-mode laser sensors, the single-mode laser sensor is proved to be a sensor with high resolution. When the PZT is driven by the analog signal （0.03 rad near 2 kHz）, the signal-to-noise ratio （SNR） of output signal from the single-mode laser sensor is close to 55 dB and the sensitivity of the sensor is about 5 ×10^-5 rad/Hz1/2.     

激光多普勒微振动信号的直接强度解调

在传统的激光多普勒测振方法中,频移信号的检测通常需要具有比较复杂的频率或相位解调系统。从激光多普勒频移和干涉理论出发,提出了一种测量振幅小于纳米量级的方法———直接强度解调法。分析了直接强度解调法的适用范围。实验中利用了迈克尔逊干涉仪结构,采用了直接强度解调的方法。对振幅约为1nm的振动信号来说,其信噪比为23dB。     

Design of 20 mm~200 mm zoom objective lens for polarization imaging system北大核心CSCD

The zoom objective lens is an important part of the polarization imaging system. At present, the zoom objective lens on the market is relatively expensive due to the use of more aspheric surfaces. In order to reduce the processing cost of the polarization imaging system zoom objective lens, a 20 mm~200 mm zoom objective lens for polarization imaging system was designed. By using positive group compensation method and Zemax to optimize the zoom system, the final system used only 7 spherical lenses to achieve good image quality. The modulation transfer function (MTF) is greater than 0.3 at 120 lp/mm, the distortion is less than 4%, and the cam curve of the system is smooth without breakpoints. The system tolerance analysis results show that the tolerance range is set as follows: the aperture tolerance of the lens surface is 2, the thickness tolerance of the lens or air center is ±0.02 mm, the inclination tolerance of the lens surface center is ±0.025°, the lens assembly and adjustment tolerance is ± 0.025 mm, and the lens refractive index deviation is 0.002. The tolerance setting conforms to the component processing and system assembly and adjustment process, which has a certain reference value to reduce the cost of polarization imaging system. © 2022 Editorial office of Journal of Applied Optics. All rights reserved.     

低噪声光纤激光器的实验研究

光传感和光通信领域的迅速发展迫切需要相位噪声和强度噪声都很低的激光光源,为满足这一需求,设计出一种新型低噪声光纤激光器。激光器采用复合腔结构,以掺铒光纤作为工作物质,通过在未被抽运的掺铒光纤中形成的瞬态自写入光纤光栅的窄带滤波特性进行选模和压窄线宽,产生稳定的单频激光输出;经过光路改进,激光输出光谱信噪比优于62 dB;利用光电负反馈电路,弛豫振荡峰下降了约25 dB,低频段强度噪声也大为改善,有效地抑制了光源的强度噪声。激光器的输出光功率大于1 dBm,线宽小于1 kHz,边模抑制比超过50 dB。优异的低噪声特性使得该激光器在光传感和光通信领域具有重要的应用价值。     

Phase boundary of the hexagonal—prism superconducting network in a magnetic field

In this paper, we systematically study the phase boundary T_c(\vec H) of a hexagonal-prism superconducting network in an external magnetic field \vec H of arbitrary magnitude and direction. The result indicates that the phase boundary of the hexagonal-prism superconducting circuit varies more sharply than that of the cubic circuit. The potential applications of the hexagonal-prism superconducting circuit are also discussed.     

外差探测系统中马卡望远镜离轴使用的研究

鉴于马卡望远镜离轴能够减小因副镜遮挡引起的光能量损失,分析了马卡望远镜离轴使用时,合作目标和非合作目标发射和接收光路的区别。讨论了马卡望远镜在外差探测系统离轴使用时,发射能量提高,但外差效率下降的原因;在合作目标外差探测系统离轴使用时发射能量提高30%以上,外差效率也有很大提高;通过对散射体目标物和平面镜的测量,分别得到了17%和85%的外差效率,验证了马卡望远镜在合作目标外差探测系统中可以离轴使用。     

Cassegrain激光发射系统的光路设计

为了提高激光探测系统激光的发射功率,在出射激光为基模的高斯光束的光路设计中,根据高斯光束经过光学系统的变换与传输特性,分析了系统采用Cassegrain望远镜时,其遮拦比以及入射光束束腰半径对光功率透过率的影响。通过具体的数值计算得出,随着遮拦比及入射光束束腰半径的增大,系统光功率透过率将减小,给出了望远镜遮拦比与发射孔径处光斑尺寸之间的最佳匹配关系,最后讨论了离焦误差（安装误差）为0.2mm时对出射光斑尺寸的影响。