Author Affiliations
Abstract
1 State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
2 Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
3 Technology Center, Huagong Laser Engineering Co., Ltd., Wuhan 430000, China
One-step precipitation of Ag nanoparticles in Ag+-doped silicate glasses was achieved through a focused picosecond laser with a high repetition rate. Absorption spectra and transmission electron microscopy (TEM) confirmed that metallic Ag nanoparticles were precipitated within glass samples in the laser-written domain. The surface plasmon absorbance fits well with the experimental absorption spectrum. The nonlinear absorption coefficient β is determined to be 2.47 × 10-14 m/W by fitting the open aperture Z-scan curve, which originated from the intraband transition in the Ag band. The formation mechanism of Ag-glass nanocomposites is discussed as well.
nonlinear optical materials laser materials processing microstructure fabrication Chinese Optics Letters
2021, 19(1): 011901
1 南昌航空大学信息工程学院, 江西南昌 330063
2 南昌航空大学测试与光电工程学院, 江西南昌 330063
红外弱小目标检测是图像处理的难点之一, 许多研究人员提出了不少检测方法。针对复杂背景与强杂波干扰下图像信杂比(Signal-to-Clutter Ratio, SCR)低造成的目前检测方法易受伪目标干扰、虚警率高的问题, 提出了一种多信息融合的红外弱小目标检测算法。首先, 构建八向局部灰度残差信息图; 其次, 设计一个滑动窗口遍历整个图像, 将图像分为一系列局部图像块, 对局部图像块的强度均值进行约束, 获得局部强度均值约束信息图; 然后, 将局部图像块进一步划分为 12个方向块, 对每个方向块中像素的梯度方向进行约束, 获取梯度方向约束信息图; 最后, 上述 3个信息图像通过点积运算得到最终显著图, 并利用阈值分割实现弱小目标的分离。将该算法与 3种其它不同算法从信杂比增益(Signal-to-Clutter Ratio Gain, SCRG)、背景抑制因子(Background Suppression Factor, BSF)以及检测率与虚警率的接受者操作特征(Receiver Operating Characteristic, ROC)曲线方面进行对比。实验结果表明: 该算法具有更高的 SCRG、BSF和 ROC曲线下面积(Area Under the Curve, AUC), 不仅能有效地抑制背景杂波、剔除伪目标, 而且能准确地检测出红外弱小目标, 具有较高的检测率。
弱小目标检测 红外图像 局部梯度 局部灰度 背景抑制 dim target detection, infrared images, local gradi
Author Affiliations
Abstract
1 China MOE Key Laboratory of Advanced Micro-structured Materials, Institute of Precision Optical Engineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
2 State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
3 University of Chinese Academy of Sciences, Beijing, 100049, China
We report the upconversion luminescence of lithium fluoride single crystals excited by an infrared femtosecond laser at room temperature. The luminescence spectra demonstrate that upconversion luminescence originates from the color center of F3+. The dependence of fluorescence intensity on pump power reveals that a two-photon excitation process dominates the conversion of infrared radiation into visible emission. Simultaneous absorption of two infrared photons is suggested to produce the F3+ center population, which leads to the characteristic visible emission. The results are on the reveal and evaluation of the simultaneous two-photon absorption on the green upconversion process.
320.2250 Femtosecond phenomena 300.6410 Spectroscopy, multiphoton 190.7220 Upconversion 160.2220 Defect-center materials Chinese Optics Letters
2016, 14(8): 083201
1 中国科学院上海光学精密机械研究所强场激光物理国家重点实验室, 上海 201800
2 中国科学院大学, 北京 100049
3 上海交通大学材料科学与工程学院, 上海 200240
4 同济大学物理科学与工程学院, 上海 200092
提出一种利用线偏振飞秒脉冲激光制备超疏水钛表面的方法。利用飞秒脉冲激光在钛片上辐照扫描诱导出表面微纳结构，以提高钛表面的粗糙度，并结合低表面能物质的超声处理得到具有超疏水特性的钛表面。通过改变飞秒脉冲激光辐照的能流密度来改变钛表面的粗糙度，得到不同润湿性能的钛表面。将制备的疏水和超疏水钛表面在大气环境中放置三个月，并对其表面润湿性能进行测量，结果表明，与三个月前相比，其表面润湿性能基本保持不变，即制备的钛表面具有稳定的疏水和超疏水性。
激光制造 飞秒激光加工 超疏水 钛表面 表面微纳结构
Author Affiliations
Abstract
1 State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences, Shanghai 201800, China
2 University of Chinese Academy of Sciences, Beijing 100049, China
3 MOE Key Laboratory of Advanced Micro-structured Materials, Institute of Precision Optical Engineering,School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
We report on the modification of the wettability of stainless steel by picosecond laser surface microstructuring in this paper. Compared with traditional methods, picosecond laser-induced surface modification provides a fast and facile method for surface modification without chemical damage and environmental pollution. As a result of treatment by 100 ps laser pulses, microstructures are fabricated on the stainless steel sample surface, contributing to the increase of the contact angle from 88° to 105°, which realizes a transformation from hydrophilicity to hydrophobicity. The morphological features of fabricated microstructures are characterized by scanning electron microscopy and optical microscopy.
Laser materials processing Laser materials processing Microstructure fabrication Microstructure fabrication Metals Metals Photonics Research
2015, 3(4): 04000180
