Coupling efficiency of single-mode fiber components using GRIN-rod lenses

This article analyzes the characteristics of single-mode fiber (SMF) components using graded-index-rod (GRIN-rod) lenses. The coupling efficiency of the SMF to GRIN-rod lens to SMF coupling system is derived in the general case. The problem is simplified by using the reciprocal field method. All solutions are in closed form. It is found that SMF position tolerance is about 3 μm; the angular tolerance is about 1°. The GRIN-rod lens position tolerance is much less critical while the angular tolerance is extremely small. These tolerances could be much less critical if the fiber is kept near the GRIN-rod lens axis.     

高稳定线性调谐GaAs基波长可调谐共振腔增强型探测器

研制了一种GaAs基波长可调谐共振腔增强型探测器. 采用分子束外延设备生长In_0.25Ga_0.75As/GaAs量子阱作为器件的有源区, 无偏压时器件的响应峰波长在1071 nm,器件在21 V的直流调谐电压下,实现了波长大于23 nm的调谐. 统计结果表明,当调谐电压大于5 V时,调谐电压与响应波长之间具有稳定、精确的对应关系, 且近似线性调谐,同时对器件响应峰的特性进行了理论分析. 关键词： GaAs 共振腔增强型探测器 高稳定 线性调谐     

单个二能级超冷原子在多个单模腔场间的共振隧穿和光子辐射

考虑单个二能级超冷原子穿过多个空间分离的单模腔场，研究原子质心运动的动能、腔长和腔间距对原子透射率和光子辐射率的影响.在腔间距等于原子质心运动de Broglie波的半波长整数倍时，结果表明，原子透射率和光子辐射率在多腔系统中出现多共振峰结构.这一结果说明，可以通过一系列腔的安排在宏观上实现对超冷原子质心运动波函数的调制. 关键词： 超冷原子 单模腔场 共振隧穿     

光纤激光陀螺系统的优化设计

分析研究了光纤激光陀螺系统的工作原理和基本构成,根据系统中各器件的性能指标对光纤激光陀螺的基本结构、性能参数进行了计算机模拟优化设计。采用双向激射双向输出结构保证光路的互易性。利用光纤环形器、掺铒光纤和光纤Bragg光栅实现滤模、选模和压缩线宽功能。针对其输出信号特点,提出利用偏振分束的方式判断陀螺工作转动方向,并最终计算陀螺转动角速度的信号处理方案。     

Experimental demonstration of single-mode fiber coupling using adaptive fiber coupler

Coupling plane wave into a single-mode fiber(SMF) with high and steady coupling efficiency is crucial for fiberbased free-space laser systems, where random angular jitters are the main influencing factors of fiber coupling. In this paper, we verified a new adaptive-optic device named adaptive fiber coupler(AFC) which could compensate angular jitters and improve the SMF coupling efficiency in some degree. Experiments of SMF coupling under the angular jitter situation using AFC have been achieved. Stochastic parallel gradient descent(SPGD) algorithm is employed as the control strategy, of which the iteration rate is 625 Hz. In closed loop, the coupling efficiency keeps above 65% when angular errors are below 80 μrad. The compensation bandwidth is 35 Hz at sine-jitter of 15 μrad amplitude with average coupling efficiency of above 60%. Also, experiments with simulated turbulence have been studied. The average coupling efficiency increases from 31.97% in open loop to 61.33% in closed loop, and mean square error(MSE) of coupling efficiency drops from 7.43% to 1.75%.     

Coupling efficiency of laser beam to multimode fiber

The coupling efficiency of laser beam to multimode fiber is given by geometrical optics, and the relation between the maximum coupling efficiency and the beam propagation factor M² is analyzed. An equivalent factor for the multimode fiber is introduced to characterize the fiber coupling capability. The coupling efficiency of laser beam to multimode fiber is calculated in respect of the ratio by the overlapping integral theory. The optimal coupling efficiency can be roughly estimated by the ratio of M² to but with a large error range. The deviation comes from the lacks of information on the detail of phase and intensity profile in the beam factor M².     

基于硅基光子器件的Fano共振研究进展

硅基光子技术的发展为新型微纳光学功能器件和片上系统提供了高可靠、高精度的实现手段.采用硅基光子技术构建的具有连续(准连续)模式微腔与离散模式的微腔耦合产生的Fano共振现象得到了广泛关注.Fano共振光谱在共振波长附近具有不对称且尖锐的谐振峰,传输光的强度在共振波长附近从0突变为1,该机制可显著提高硅基光开关、探测器、...     

Experimental Study of MQW RCE Photodetector

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The Optimum Coupling Coefficient of Optically Pumped NH3 Far-Infrared Cavity Laser

Based on the semiclassical density matrix theory, the optimum output power reflection coefficient (coupling coefficient) of output coupler for optically pumped NH₃ far-infrared (FIR) cavity laser was calculated by means of iteration method. Experimentally, FIR Fabry-Perot cavity laser was designed and constructed by using inductive metallic meshes as couplers, and the measurement showed that the theoretical calculation were in agreement with experimental results.     

空间激光与单模光纤和光子晶体光纤的耦合效率

为了设计最优光纤耦合系统,利用高斯模场近似单模阶跃光纤的模场和大模面积光子晶体光纤的模场,推导出了理想情况下空间激光与这两种光纤的耦合效率解析表达式以及光纤端面相对于耦合系统存在横向偏移和端面倾斜时的耦合效率解析表达式。基于上述理论表达式计算了空间激光与光纤的耦合效率,并通过实验验证了此理论表达式的有效性。理论计算和实验均证实了单模阶跃光纤对于横向偏移更敏感,当横向偏移量等于单模光纤的纤芯半径时所对应的耦合效率只有20.25%,为理论最大值的1/4;而大模面积光子晶体光纤对于端面倾斜更加敏感,当端面倾斜2°时对应的耦合效率只有40.5%,为理论最大值的1/2。所提出理论表达式和实验方法完全可以为设计光纤耦合系统提供准确的参数。     

用多极理论分析圆桩对称微波谐振腔

用多极理论计算具有复杂几何形状、圆柱对称微波腔的谐振频率,推导出用多极理论计算圆柱对称微波腔谐振频率的本征值方程。三个工程实例的计算结果表明,用多极理论计算圆柱对称微波腔谐振频率,不仅具有较高的计算精度,而且可以很方便地应用于复杂几何形状圆柱对称微波腔工程问题的设计与计算,多极理论是计算圆柱对称微波腔谐振频率的一种有效方法。     

用多极理论分析圆柱对称微波谐振腔

用多极理论计算具有复杂几何形状、圆柱对称微波腔的谐振频率,推导出用多极理论计算圆柱对称微波腔谐振频率的本征值方程。三个工程实例的计算结果表明,用多极理论计算圆柱对称微波腔谐振频率,不仅具有较高的计算精度, 而且可以很方便地应用于复杂几何形状圆柱对称微波腔工程问题的设计与计算,多极理论是计算圆柱对称微波腔谐振频率的一种有效方法。     

用多极理论分析圆柱对称微波谐振腔

 用多极理论计算具有复杂几何形状、圆柱对称微波腔的谐振频率,推导出用多极理论计算圆柱对称微波腔谐振频率的本征值方程。三个工程实例的计算结果表明,用多极理论计算圆柱对称微波腔谐振频率,不仅具有较高的计算精度, 而且可以很方便地应用于复杂几何形状圆柱对称微波腔工程问题的设计与计算,多极理论是计算圆柱对称微波腔谐振频率的一种有效方法。     

利用互补天线原理求解孔缝的共振性能

 利用互补天线原理从理论上推导了真空、介质窄缝的共振频率公式,在理想窄缝长度小于5倍波长、辐射角度偏离垂直方向小于30°的情况下,孔缝的共振频率点仍然可以用半波振子的辐射情况来解释,共振点满足孔缝长度等于入射波的半个波长;介质窄缝等效为半个孔缝深度的微带贴片天线,不同介电常数介质填充时的共振频率理论公式推导值和数值模拟值基本一致,相对误差在5%以内。进一步分析了窄缝阵列的耦合性能,结果表明互补天线原理可以很好地应用于分析和求解孔缝的共振性能。     

选频元件对光纤激光器自组织相干合成的影响

采用不同中心谱线、不同谱线宽度的选频元件进行实验,研究选频元件谱线特性对相干合成效率的影响。实验表明：选频元件中心谱线越接近,相干合成效率越高;与此同时,选频元件的谱线宽度越宽,线形越接近重合,相干合成效率也越高,接近理想值100%。在此基础上,利用中心谱线一致的宽谱选频元件,实现两路掺Er光纤激光器的相干合成,输出功率为375 mW,相干合成效率高达99.3%。     

单模光纤中三阶色散对超短光脉冲传输的影响

基于超短光脉冲在单模光纤中传输时高阶非线性效应的影响。应用非线性薛定谔方程(HONLS)理论,考虑光纤色散三阶效应,推导出无啁啾的高斯脉冲沿光纤传输时脉冲变化的表达式,并对理论结果进行了数值模拟与分析。结果表明,三阶色散会引起光脉冲形状发生畸变,会在其前沿或后沿附近形成非对称的振荡结构。     

Theoretical and experimental study on rare-eath element-doped silicon single-mode fiber laser with two different structures of resonators

Abstract: Laser resonator is very important in the study and fabrication of lasers. The work conditions and work parameters of rare-earth element-doped optical fiber lasers with two different structures of laser resonators, i. e., the fiber ring resonator and Fabry-Perot resonator are studied. The fineness, laser resonant conditions, laser oscillation conditions and threshold inversion of these two different cavity are deduced. A series of experiments are also given. The result is very valuable to evaluate the output of optical fiber laser and can be a foundation of device fabrication. The Nd~(3 )-doped silica single-mode fiber laser pumped by Ar~ laser with a low threshold of 1.02 mW and a maximum output of more than 1 mW are presented in this paper.     

选频元件对光纤激光器自组织相干合成的影响

采用不同中心谱线、不同谱线宽度的选频元件进行实验,研究选频元件谱线特性对相干合成效率的影响。实验表明:选频元件中心谱线越接近,相干合成效率越高;与此同时,选频元件的谱线宽度越宽,线形越接近重合,相干合成效率也越高,接近理想值100%。在此基础上,利用中心谱线一致的宽谱选频元件,实现两路掺Er光纤激光器的相干合成,输出功率为375 mW,相干合成效率高达99.3%。     

Characterization of single-polarization single-mode photonic crystal fiber using full-vectorial finite element method

A modal solution approach based on the powerful, finite element method (FEM) using a full-vectorial H-field formulation has been used to determine the single-mode operation of a photonic crystal fiber (PCF). The modal solution of the fundamental space-filling mode has also been obtained to identify the cutoff conditions of the waveguide modes. The FEM, with the perfectly matched layer boundary condition, has been developed and employed to characterize the leakage loss and the differential loss between the polarized modes of a PCF. The design approach for a single-polarization and single-mode PCF has also been discussed.