In this paper,based on the analysis of the operation characteristics of laser diode end-pumped laser crystal,a thermal model of laser diode end-pumped Tm∶YAG crystal rod is established.The temperature field,thermal stress field and end-pumped crystal rod are numerically calculated by finite element method using heat conduction theory.The effects of laser beam with different laser energy distribution(circular Gaussian spot,elliptical Gaussian spot,cir-cular flat top spot,square flat top spot),pump spot radius and Tm3+doping concentration on the temperature field dis-tribution and end surface shape variables of laser rod are analyzed,and plotted in three-dimensional distribution dia-grams.The results show that under the stable state,if the laser diode pump power is 30 W,and the pump spot radius is 400 μm,the maximum temperature rise of the pump surface of the Tm∶YAG crystal rod with the doping concentration of 3.5at.％is 124.55℃,and the maximum stress of the pump surface is 209 MPa along the crystal z axis.The maxi-mum heat shape variable of the pump surface is 0.888 pm.This study provides theoretical guidance for the design of Tm∶YAG laser.
The mid-infrared 2 mu m band solid-state laser has a wide range of applications in the fields of industry, military, medical, and scientific research. Single-doped holmium solid-state laser is an important method to produce 2 mu m lasers. 2 mu m lasers can also provide an effective pump source for mid-infrared optical parametric oscillator. This paper introduces the advantages of single-doped holmium solid-state laser, and summarizes the research progress of single-doped holmium solid-state lasers based on various substrates in the past decades. Finally, the future development prospect of single-doped holmium solid-state lasers is prospected.
基于荧光光谱理论,结合弱光探测技术及等离子体放电技术,搭建了一套兼具臭氧制备及标定性能的CO物质浓度检测系统,并借助实验手段对CO化学发光规律进行了定量探究,旨在进一步揭示CO+O3 化学发光反应机理.结果表明,在常温下,当CO与 1345 ppm臭氧混合时,CO主要是与O原子而非臭氧分子发生化学激发行为,生成激发态分子,由于O原子寿命较短,当CO浓度较低时,CO浓度-化学发光光强存在较强的线性关系,R2＞0.99,当CO浓度较高时,非线性效应变强,探测光强变化速率随CO浓度增加而变大.
To address the problem that manually extracted features are not sensitive to infrared targets, resulting in inaccurate tracking of infrared targets, a UAV infrared target tracking algorithm is proposed in the framework of fully-convolutional Siamese networks, fusing multi-layer depth features and combining with channel perception.Firstly, the pre-training network is used to extract the target depth feature, and the Conv4-1,Conv4-3 and Conv5-2 layers of the target to be tracked are extracted respectively.Then, the feature channels that are more sensitive to the target activity and scale changes are selected through gradient calculation to participate in the subsequent cross-correlation operation, and the target response map is obtained by calculating the similarity between the template image and the candidate region search image.Finally, the average peak correlation energy（APCE）is used to evaluate the tracking results, and the Kalman filter is used to correct the tracking results.The performance test is carried out on the LSOTB-TIR infrared target tracking data set, and compared with the current nine excellent algorithms.The experimental results show that the algorithm in this paper has the highest tracking success rate, can effectively deal with the challenges of thermal crossover and distractor in infrared target tracking, and has better real-time performance.
基于螺旋谱理论推导出矢量涡旋光束在斜程大气湍流传输中的轨道角动量(orbital angular momentum,OAM)谱,讨论了修正Kolmogorov大气湍流对不同阶矢量涡旋光束光场分布及光束OAM谱的影响.利用旋转毛玻璃作为随机相位屏,实验采集了矢量涡旋光束通过旋转毛玻璃后的光强图像与归一化强度.结果表明:经大气湍流斜程传输后,矢量涡旋光束的光强分布产生畸变且OAM谱发生弥散,OAM谱弥散程度随传输距离的增大而增大.传输距离不变时,天顶角越大,主OAM模相对功率越小,湍流内尺度减小与折射率结构常数增大均会导致主OAM模相对功率减小.同一传输路径下,随着湍流强度的增大,矢量涡旋光束中心相位奇点的强度逐渐增大,并且拓扑荷不变时,偏振阶数高的矢量涡旋光束受到的湍流影响较小.
