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Characteristics and suppression of beam distortion in a high repetition rate nanosecond stimulated Brillouin scattering phase conjugation mirror

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High Power laser Science and Engineering 2024年第2期12卷 69-78页

作者： Yifu Chen Bowen Tan Duo Jin Bin Chen Zhenxu Bai Kun Wang Yulei Wang zhiwei lü School of Astronautics Harbin Institute of TechnologyHarbinChina Center for Advanced laser Technology Hebei University of TechnologyTianjinChina Hebei Key laboratory of Advanced laser Technology and Equipment TianjinChina School of Energy and Environmental Engineering Hebei University of TechnologyTianjinChina

The stimulated Brillouin scattering phase conjugation mirror (SBS-PCM) based on liquid media is widely used in high-power laser systems due to its robust thermal load capacity, high energy conversion efficiency and improved beam quality. Nevertheless, with an increase in the pump repetition rate, thermally-induced blooming and optical breakdown can emerge, leading to distortions in the Stokes beam. In this study, we delved into the thermal effects in liquid SBS-PCMs employing hydrodynamic analysis, establishing a relationship between beam profile distortion and the thermal convection field. We calculated the temperature and convection velocity distribution based on the pump light parameters and recorded the corresponding beam profiles. The intensities of the beam profiles were modulated in alignment with the convection directions, reaching a velocity peak of 2.85 mm/s at a pump pulse repetition rate of 250 Hz. The residual sum of squares (RSS) was employed to quantify the extent of beam profile distortion relative to a Gaussian distribution. The RSS escalated to 7.8, in contrast to 0.7 of the pump light at a pump pulse repetition rate of 500 Hz. By suppressing thermal convection using a high-viscosity medium, we effectively mitigated beam distortion. The RSS was reduced to 0.7 at a pump pulse repetition rate of 500 Hz, coinciding with a twentyfold increase in viscosity, thereby enhancing the beam quality. By integrating hydrodynamic analysis, we elucidated and mitigated distortion with targeted solutions. Our research offers an interdisciplinary perspective on studying thermal effects and contributes to the application of SBS-PCMs in high-repetition-rate laser systems by unveiling the mechanism of photothermal effects.

关键词： beam profile high power high repetition rate stimulated Brillouin scattering phase conjugation mirror thermal convection

Novel optical fiber current sensor based on magnetic fluid

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Chinese Optics letters 2010年第4期8卷 392-394页

作者：胡涛赵勇李星陈菁菁吕志伟 Department of Automatic Testing and Control Harbin Institute of Technology College of Information Science and Engineering Northeastern University

A novel fiber optic Fabry-Perot（F-P） current sensor is developed based on magnetic fluid as the medium in F-P interference cavity.A signal demodulation method based on slanted fiber Bragg grating（FBG） wavelength measurement system is *** and principle of electromagnetic-controlled refractive index of the magnetic fluid is described,as well as the structure of the sensor *** experiments are carried out,and the results indicate that there is a fairly good linearity of the measurement *** thickness of magnetic fluid film and initial concentration will affect the measurement results.

关键词： Fiber Bragg gratings Optical fibers Optical materials Refractive index Sensors

linewidth narrowing in free-space-running diamond Brillouin lasers

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High Power laser Science and Engineering 2023年第4期11卷 25-32页

作者： Duo Jin Zhenxu Bai Zhongan Zhao Yifu Chen Wenqiang Fan Yulei Wang Richard P.Mildren zhiwei lü Center for Advanced laser Technology Hebei University of TechnologyTianjinChina Hebei Key laboratory of Advanced laser Technology and Equipment TianjinChina MQ Photonics Research Centre Department of Physics and AstronomyMacquarie UniversitySydneyAustralia

This study analyzes the linewidth narrowing characteristics of free-space-running Brillouin lasers and investigates the approaches to achieve linewidth compression and power enhancement *** results show that the Stokes linewidth behavior in a free-space-running Brillouin laser cavity is determined by the phase diffusion of the pump and the technical noise of the ***,a Stokes light output with a power of 22.5 W and a linewidth of 3.2 kHz was obtained at a coupling mirror reflectivity of 96%,which is nearly 2.5 times compressed compared with the linewidth of the pump(7.36 kHz).In addition,the theorical analysis shows that at a pump power of 60Wand a coupling mirror reflectivity of 96%,a Stokes output with a linewidth of 1.6 kHz and up to 80%optical conversion efficiency can be achieved by reducing the insertion loss of the *** study provides a promising technical route to achieve high-power ultra-narrow linewidth special wavelength laser radiations.

关键词： high power narrow linewidth single-frequency laser stimulated Brillouin scattering

A 115 ps,100 Hz high-beam-quality laser based on transient stimulated Brillouin scattering pulse compression

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High Power laser Science and Engineering 2023年第6期11卷 39-46页

作者： Jianfeng Yue Yulei Wang Mengyu Jia Kai li Chen Cao Yu Yu Yunfei li zhiwei lü Center for Advanced laser Technology Hebei University of TechnologyTianjinChina Hebei Key laboratory of Advanced laser Technology and Equipment TianjinChina

This work demonstrates the generation of short pulse duration and high-beam-quality laser pulses using transient stimulated Brillouin scattering at a high repetition *** effects and optical breakdown are identified as the main factors that restrict energy reflectivity and beam quality under high repetition rates and transient *** experimental analysis,the interaction length and focal point size are determined to be the key parameters in reducing the thermal effect by reducing the absorption of the laser pulse by the *** obtained results show that pulses with a duration of 175 ps and beam quality M^(2)of around 1.2 can be achieved with a maximum energy reflectivity of over 40%under an interaction length of 50 ***,at an interaction length of 90 mm,a pulse output with a minimum duration of 115 ps(0.5τQ)is achieved.

关键词： high beam quality high energy nonlinear optics stimulated Brillouin scattering

基于多尺度残差双域注意力网络的乳腺动态对比度增强磁共振成像肿瘤分割方法

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电子与信息学报 2023年第5期45卷 1774-1785页

作者：刘侠吕志伟李博王波王狄哈尔滨理工大学哈尔滨150080 黑龙江省复杂智能系统与集成重点实验室哈尔滨150080 广东科学技术职业学院计算机工程技术学院(人工智能学院) 珠海519090

针对乳腺肿瘤大小形态多变、边界模糊以及前景与背景间严重类不平衡的问题,该文提出一种多尺度残差双域注意力融合网络。该网络以多尺度卷积构成的多尺度残差块作为基本搭建模块,通过提取多尺度特征和优化梯度传播通道提高其识别不同尺... 详细信息

针对乳腺肿瘤大小形态多变、边界模糊以及前景与背景间严重类不平衡的问题,该文提出一种多尺度残差双域注意力融合网络。该网络以多尺度卷积构成的多尺度残差块作为基本搭建模块,通过提取多尺度特征和优化梯度传播通道提高其识别不同尺寸目标的能力,同时融入双域注意力单元,提高网络的边缘识别和边界保持能力。另外该文提出一种混合自适应权重损失函数改善网络优化方向,缓解正负样本极度不均衡的影响。实验结果表明,该文所提方法的平均骰子相似系数(Dice)值达到0.8063,较U形网络(UNet)提高5.3%,参数量下降73.36%,具有更优的分割性能。

关键词：乳腺肿瘤分割多尺度残差块双域注意力混合自适应权重损失函数

铟置换液制备聚硅酸氯化铝及其对印染废水的处理

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化工环保 2010年第3期30卷 246-249页

作者：吕志伟杨阳河北工程大学城市建设学院河北邯郸056038 河北工程大学理学院河北邯郸056038

以铟置换液和工业水玻璃为原料,以盐酸为活化剂和调节剂制备聚硅酸氯化铝絮凝剂。考察了聚硅酸氯化铝制备过程中各因素对印染废水处理效果的影响。实验确定的最佳工艺条件为铝硅比(铝与硅的质量比)为1、聚合pH为1.6、聚合时间为12h、聚... 详细信息

以铟置换液和工业水玻璃为原料,以盐酸为活化剂和调节剂制备聚硅酸氯化铝絮凝剂。考察了聚硅酸氯化铝制备过程中各因素对印染废水处理效果的影响。实验确定的最佳工艺条件为铝硅比(铝与硅的质量比)为1、聚合pH为1.6、聚合时间为12h、聚合温度为25℃。用在此条件下制备出的聚硅酸氯化铝絮凝剂处理印染废水,印染废水脱色率可达95%以上。

关键词：铟置换液聚硅酸氯化铝絮凝剂脱色印染废水综合利用废水处理

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一种基于傅里叶变换的分析载波条纹的新方法

光学学报 2006年第8期26卷 1167-1171页

作者：王雨雷吕志伟王岩何伟明哈尔滨工业大学光电子技术研究所哈尔滨150001

针对传统傅里叶变换法处理光载波干涉条纹图时会有边缘效应产生的问题,提出了一种基于傅里叶变换法的外推延拓方法,并从理论上进行了数学推导。为了验证这种方法的正确性,分别对一维数字信号和二维空间载波条纹图进行了数值模拟,进一步... 详细信息

针对传统傅里叶变换法处理光载波干涉条纹图时会有边缘效应产生的问题,提出了一种基于傅里叶变换法的外推延拓方法,并从理论上进行了数学推导。为了验证这种方法的正确性,分别对一维数字信号和二维空间载波条纹图进行了数值模拟,进一步分析了误差产生的原因,并与传统的傅里叶变换法对比。结果表明该法可以有效抑制传统傅里叶变换法处理光载波干涉条纹图时边缘效应所造成的较大误差,在基于空间域相位调制技术的波面干涉测量中,对空间载波条纹图进行处理,可以使相位的计算精度达到3.3 mrad。

关键词：光学测量外推延拓傅里叶变换载波干涉条纹

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铟置换液制备聚硅酸氯化铝及其脱色性能研究

工业水处理 2008年第11期28卷 47-49页

作者：黎铉海吕志伟区军广西大学化学化工学院广西南宁530004 广西特种设备监督检验院广西南宁530002

以铟置换液(Al2O3质量分数为5.35%)和工业水玻璃为原料,以盐酸为活化剂和调节剂制备聚硅酸氯化铝絮凝剂,考察了聚硅酸氯化铝制备过程中铝硅比、pH、温度和陈化时间对脱色性能的影响。其优化工艺条件为:铝硅比为1,pH为1.8,聚合温度30℃,... 详细信息

以铟置换液(Al2O3质量分数为5.35%)和工业水玻璃为原料,以盐酸为活化剂和调节剂制备聚硅酸氯化铝絮凝剂,考察了聚硅酸氯化铝制备过程中铝硅比、pH、温度和陈化时间对脱色性能的影响。其优化工艺条件为:铝硅比为1,pH为1.8,聚合温度30℃,聚合时间14 h。在此条件下制得铝质量分数为1.13%、盐基度为51%的聚硅酸氯化铝净水剂,其对蔗渣造纸中段废水的脱色率为95%以上。

关键词：聚硅酸氯化铝脱色率铟

激光冲击强化中的激光变量——研究进展和拓展空间

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激光与光电子学进展 2024年第5期61卷 36-46页

作者：周罗贤朱成禹远航吕志伟哈尔滨工业大学可调谐(气体)激光技术国家级重点实验室黑龙江哈尔滨150080

在激光冲击强化(lSP)技术中,作为冲击载荷的驱动源头和能量来源,激光脉冲参数的不同选取决定着激光吸收机制取向、能量沉积程度乃至等离子爆炸行为规律的差异,进而对冲击载荷形态特征和材料表面强化效果产生重要的决定作用。本文对目前... 详细信息

在激光冲击强化(lSP)技术中,作为冲击载荷的驱动源头和能量来源,激光脉冲参数的不同选取决定着激光吸收机制取向、能量沉积程度乃至等离子爆炸行为规律的差异,进而对冲击载荷形态特征和材料表面强化效果产生重要的决定作用。本文对目前lSP技术中涉及的各类激光参数在激光驱动冲击效应中的作用机理、影响规律,以及在工艺配给上的研究和认知现状进行了综述。针对激光时域结构在决定等离子体膨爆行为和冲击载荷特征中的重要性,以及目前lSP普遍采用调Q激光器高斯时间波形的技术现状展开评述,并指出通过优化激光脉冲时域结构来提升光能向机械能的转换效率,或通过调节激光时域参数来实现精准操控冲击载荷特征具有可能性。

关键词：激光技术激光冲击强化表面处理激光诱导冲击波激光时域结构