Abstract ：

三维显微测振仪可用于测量微结构的三维振动，其两条离轴光路用于接收包含面内振动信息的信号光，系统的机械形变会直接影响光纤的耦合效率，从而影响系统的测振精度。结合衍射传播理论和光纤耦合原理，建立了离轴光路的信号光传输耦合模型，针对信号光平面与光纤平面存在倾角的问题，利用频域坐标旋转变换法将倾斜的物面信号光场投影到平行的参考平面上，再基于菲涅耳衍射传播计算得到光纤平面的光场分布，进而结合光纤的模场分布可计算得到光纤耦合效率。研究了耦合透镜、光纤等元件的机械形变对光纤耦合效率的影响，阐明了光纤耦合效率和各个机械变形量的关系，为三维激光多普勒显微测振系统的设计和装调工作提供了理论指导。

Keyword ：

光纤耦合 三维显微测振 干涉测量 衍射传播理论 测量 机械形变

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Abstract ：

Objective Three-dimensional (3D) laser Doppler micro-vibration measurement technology is widely applied in the research on dynamic characteristics of microstructures. Its two off-axis optical paths are employed to receive signal light containing in-plane vibration information. The optical fiber coupling efficiency in optical paths will directly affect the vibration measurement accuracy of the system. At present, the factors affecting the coupling efficiency of optical fiber mainly include optical system aberration, atmospheric turbulence, amplitude distribution type of signal light and local light, and optical system parameters. The effect of gravity, temperature, or mechanical deformation of optical elements during installation on the coupling efficiency is not considered. In addition, most of the current research focuses on one-dimensional laser Doppler detection system, and there is a lack of research on 3D laser Doppler micro-vibration measurement system, especially the off-axis optical path. To this end, based on the diffraction propagation theory and the fiber coupling principle, the optical transmission and coupling model of the off-axis signal receiving optical path in the 3D micro-vibration measurement system is built in this paper. The mechanical deformation of typical optical components in the system is analyzed, and the influence of these mechanical deformations on the fiber coupling efficiency is studied. In addition, the maximum tolerances of different mechanical deformations are given. The research is of guiding significance for the design and installation of 3D laser Doppler micro-vibration measurement system. Methods The detection optical path of the 3D micro-vibration measurement system includes the main axis optical path and off-axis optical path. The main axis optical path is overlapped with the z axis. Its function is to incident the laser onto the object to be measured and receive the reflected signal light containing the vibration component information of the object in the z direction. The two off-axis optical paths are in the y-z plane and the x-z plane respectively, and the angle between them and the main axis optical path is 40° . They are employed to receive the reflected signal light containing the information of the vibration component of the object in the x and y directions. The object plane is inclined to the off-axis coupling lens plane, so the diffraction propagation between the two inclined planes needs to be considered. In this paper, the optical transmission model of the off-axis signal is built. Firstly, the optical field of the original object plane signal is projected onto the reference plane parallel to the coupling lens plane by the frequency domain coordinate rotation transformation method. Secondly, the optical field distribution of the reference surface is propagated to the coupling lens plane through diffraction, and then to the fiber plane through the phase modulation of the coupling lens. Subsequently, the optical field distribution on the fiber plane can be obtained. Finally, the ideal fiber coupling efficiency can be calculated by the mode field matching method combined with the mode field distribution of single-mode fiber. The relationship between different mechanical deformations and the coupling efficiency of optical fiber is obtained by analyzing the change of parameters in the coupling model of off-axis signal caused by different mechanical deformations. Results and Discussions The relationship between mechanical deformation and fiber coupling efficiency is obtained by the coupling model of off-axis signal optical transmission. Firstly, the relationship between the eccentricity of the coupling lens and the coupling efficiency is studied (Fig. 4). When the coupling efficiency is better than 40%, the maximum allowable range of the offset is about ±1. 5 μm. When the beam passes through the tilted coupling lens, the wavefront changes caused by the tilt of the lens near the front and rear surfaces cancel each other out. Therefore, the tilt of the coupling lens exerts no effect on the coupling efficiency if the aberration of the coupling lens is ignored. Next, the influence of the fiber misalignment and the fiber misalignment angle on fiber coupling efficiency is studied. The fiber coupling efficiency is more sensitive to the optical fiber misalignment in the x-y direction [Fig. 6(a)] and less sensitive to the optical fiber misalignment in the z direction [Fig. 6(b)], and the change with the optical fiber misalignment angle is less obvious (Fig. 8). In addition, the out-of-plane vibration caused by the object under test will also affect the fiber coupling efficiency of the off-axis optical path (Fig. 10). When the out-of-plane vibration displacement is within the range of ±3 μm, the coupling efficiency slowly decreases from 76. 5% to about 60. 0%, which is acceptable in the actual utilization of the system. Conclusions A coupling model of optical transmission and transmission of off-axis signals in a 3D laser Doppler microvibration measurement system is built. The effect of mechanical deformation on the optical coupling efficiency of off-axis signals in the system is further studied. The simulation results show that the off-axis optical coupling efficiency is sensitive to the coupling lens offset and the optical fiber misalignment. Under the micron displacement error, the off-axis coupling efficiency decreases sharply. Therefore, the two mechanical errors should be avoided first during the system design. The optical coupling efficiency of the off-axis signal is less sensitive to the defocus of fiber and the fiber misalignment angle. When the actual system is adopted, if the out-of-plane vibration range of the object to be measured is ±3 μm, the coupling efficiency of the off-axis signal light slowly decreases from 76. 5% to about 60. 0%, which has little influence on the system. When the aberration of the coupling lens is ignored, the coupling efficiency is not affected by the coupling lens tilt. This study is of guiding significance for the design of off-axis detection optical path of 3D laser Doppler micro-vibration measurement system. The diffraction propagation calculation and the construction and analysis of the coupling model can be further extended to other single-mode fiber imaging systems. © 2023 Chinese Optical Society. All rights reserved.

Keyword ：

fiber coupling interferometry three-dimensional micro-vibration measurement mechanical deformation measurement diffraction propagation theory

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Abstract ：

薄膜铌酸锂波导与单模光纤在模场尺寸上存在很大差异,模场失配严重,导致两者直接耦合的效率低下。针对薄膜铌酸锂波导与超高数值孔径(ultrahigh numerical aperture,UHNA)光纤的端面耦合问题,基于时域有限差分法(finite difference time domain method,FDTD)优化设计了反向锥形端面耦合器的结构参数,仿真实现了薄膜铌酸锂矩形波导与UHNA光纤的高效耦合。利用电子束曝光、电感耦合等离子体刻蚀等工艺,制备了反向锥形耦合器,设计并建立了端面耦合测试平台,完成了反向锥形耦合器的性能测试。实验结果表明,反向锥形耦合器近场输出光斑在水平和垂直方向的模场直径分别3.3和3.6μm,水平和垂直方向的3 dB对准容差分别为3.0和3.2μm,单端插入损耗为6.24 dB/面,表明设计制作的反向锥形耦合器具有较好的耦合性能。该研究为大容量、高速率的集成光子器件与光纤之间的耦合提供了高耦合效率的光接口方案。

Keyword ：

光波导 端面耦合 反向锥形耦合器 超高数值孔径光纤 薄膜铌酸锂 时域有限差分法

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Abstract ：

本发明公开了一种薄膜铌酸锂器件的耦合装置及耦合方法，包括：沿激光器的激光出射方向依次设置的第一准直透镜、第一汇聚透镜、薄膜铌酸锂器件、第二准直透镜、第二汇聚透镜和光纤；激光器出射的激光经第一准直透镜准直成第一平行光；第一平行光经第一汇聚透镜汇聚，并耦合进入薄膜铌酸锂器件；薄膜铌酸锂器件的出射光经第二准直透镜准直成第二平行光；第二平行光经第二汇聚透镜汇聚，并耦合进入光纤，实现薄膜铌酸锂器件与光纤的耦合。相比于传统在薄膜铌酸锂器件上制作模斑转换器，本发明的工艺更简单、且大大提升光纤到波导的耦合效率，而且良率也得到了明显的提升。

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Abstract ：

本发明公开了一种连续介质相干阵边发射半导体激光器及制备方法，包括：导电衬底、形成于导电衬底上表面的外延层以及位于外延层两侧的后端光学介质波导区和前端光学介质波导区；外延层的上表面设置有一维阵列脊波导区；后端光学介质波导区上刻蚀得到后端相位光栅层，前端光学介质波导区上刻蚀得到前端相位光栅层；一维阵列脊波导区的上表面设置P面电极，导电衬底的下表面设置N面电极，后端相位光栅层的端面设置高反膜，前端相位光栅层的端面设置增透膜。本发明的激光器无需外部光学元件对超模的选择便可实现同相模激射，并且光场在远场慢轴方向具有超窄发散角，大大提高了阵列半导体激光器与光纤的耦合效率。

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本发明公开了一种并联耦合自成像外腔相干阵半导体激光器，包括：半导体激光芯片阵列、通光介质层和外腔反射层；半导体激光芯片阵列包括多个发光单元，通光介质层和外腔反射层构成激光自成像外腔；半导体激光芯片阵列出光面的非发光区域镀有高反射膜，高反射膜使半导体激光芯片阵列边缘处由于自成像不完全而导致无法注入至发光单元的反馈光可在自成像外腔中多次振荡，以重新形成可完全注入到发光单元中的自成像。本发明提高了发光区域外激光的注入，可将芯片阵列中包括边缘在内的所有发光单元高效并联耦合，消除自成像外腔反馈产生的芯片阵列边缘效应，增强自成像外腔反馈效率，获得高并联耦合效率、高效光互注入的相干阵激光输出。

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Abstract ：

本发明公开了一种薄膜铌酸锂光学耦合结构及装配耦合方法，包括：薄膜铌酸锂波导、光纤、棱镜、光学透镜和接收套件；薄膜铌酸锂波导的一侧放置有光纤，使光纤输出的光耦合进入薄膜铌酸锂波导内；薄膜铌酸锂波导的另一侧放置有棱镜，棱镜与薄膜铌酸锂波导的接触位置处设有匹配液，棱镜的出光方向上依次放置有光学透镜和接收套件；使薄膜铌酸锂波导内传输的光耦合进入到棱镜内，并经光学透镜汇聚进入到接收套件中。本发明采用棱镜与薄膜铌酸锂波导耦合，大大提高了薄膜铌酸锂的耦合效率，耦合效率较模斑转换器提升了20～40％，且操作简单。

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Abstract ：

在半导体激光器的光纤耦合系统中,bar条的各发光点指向偏差(偏向角)会恶化光束整形效果,显著降低光纤耦合效率。针对该现象提出利用引入修正角的楔形整形镜补偿发光点的指向偏差,改善激光束的指向性和光束整形效果。通过ZEMAX软件模拟与实验验证,在光纤耦合系统中使用引入修正角后的楔形整形镜片,其整形效果显著改善,测量的光束参数积(BPPs)在快轴和慢轴方向分别为7.25 mm·mrad和5.05 mm·mrad,聚焦光斑为148μm×135μm(包含90%能量)。该系统将单个bar条耦合进芯径200μm、数值孔径(NA)0.2的光纤中,在注入电流60 A时,获得稳定输出功率53 W,对应电-光转换效...

Keyword ：

楔形整形镜 半导体激光器 光束整形 光纤耦合

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针对矩形阵列光束与光纤耦合的角度填充系数低,以及未能充分利用光纤数值孔径的缺点,提出密堆积阵列光束的光纤耦合方式以最大化角度填充系数,从而提升光纤耦合的输出亮度。基于该排布方式设计无像差平行平板缩束装置,相比于望远镜缩束系统,该装置可保持光束发散角不变,消除阵列光束之间的暗区,改善组合光束的光束质量。仿真结果表明,该装置可将14支功率为1.5 W绿光单管耦合进数值孔径为0.15和芯径为105μm的光纤中,获得93.75%的光纤耦合效率,输出功率为19.13 W,对应亮度为3.125 MW·cm~(-2)·Sr~(-1),系统的总光-光传输效率达91.10%。

Keyword ：

高亮度 光束整形 半导体激光器 激光光学 绿光

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Abstract ：

针对半导体激光阵列的发光单元指向性偏差导致快轴光束质量显著劣化的现象,研究了发光单元指向性偏差对快轴光束质量的影响,提出了一种利用微光学元件补偿发光单元指向性偏差的方法,设计了一种楔形微透镜阵列,可实现单个bar条的光束耦合进芯径200μm、NA=0.2的光纤.模拟计算结果表明,楔形微透镜阵列的补偿作用可使半导体激光阵列快轴方向的光参数积由64.24 mm·mrad下降到58.14 mm·mrad,光纤耦合效率达到95.6％,相比补偿前提高了10.4％.为降低工艺难度,采用分类补偿的方法,模拟光纤耦合效率达到91.5％.考虑到工业应用,采用由三片楔形透镜组成的透镜组对分类后的发光单元光束分别进行补偿,测量得到的光纤耦合效率为90.4％,比补偿光束指向性之前的耦合效率提高了约7％.

Keyword ：

发光单元指向性 光束质量 楔形微透镜 半导体激光阵列

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