A photonic wire-based directional coupler based on SOI

A photonic wire-based directional coupler based on SOI was fabricated by e-beam lithography (EBL) and the inductively coupled plasma (ICP) etching method. The size of the sub-micron waveguide is 0.34 μm × 0.34 μm, and the length in the coupling region and the separation between the two parallel waveguides are 410 and 0.8 μm, respectively. The measurement results are in good agreement with the results simulated by 3D finite-difference time-domain method. The transmission power from two output ports changed reciprocally with about 23 nm wavelength spacing between the coupled and direct ports. The extinction ratio of the device was between 5 and 10 dB, and the insertion loss of the device in the wavelength range 1520-1610 nm was between 22 and 24 dB, which included an about 18.4 ± 0.4 dB coupling loss between the taper fibers and the polished sides of the device.     

Effects of third-order dispersion on soliton switching in fiber nonlinear directional couplers

The split-step Fourier method is used to study the energy switching characteristics of fiber nonlinear directional couplers with the third-order dispersion. The effects of the third-order dispersion increases with the third-order dispersion coefficient and input power and result in pulse shift and energy decreases. Adding high-order nonlinear can partly overcomes these effects.     

Design of a capacitive main power coupler for RF superconducting accelerators

An updated main coupler has been designed for the superconducting accelerator of Free Electron Laser (FEL) project under construction in Peking University. A capacitive structure is chosen for the main coupler. Numerical investigation using CST Microwave Studio demonstrates the cold window part. The other nonstandard structures such as holding rods and antenna are also optimized. The coupler uses a 95% purity Al₂O₃ ceramic cold window. The VSWR (Vottage Standing Wave Ratio) is 1.02 at 1.3GHz and the frequency bandwidth is 45MHz with VSWR<1.1. The electric field intensity is 8.5×10^－2kV/mm around the window with 20kW Continuous Wave (CW) transmitted power. The Q_ext is designed variable from 5×10⁶ to 1×10⁷.     

神经网络在棱镜摄谱仪定量分析光谱中的应用

给出了采用BP神经网络拟合标准光源在棱镜摄谱仪的谱平面位置和相应波长的非线性函数,省去了和标准铁谱比对测量未知谱线波长,简化了光谱的定量分析,提高了仪器的自动化和智能化水平.     

一种确定光纤传感器中3×3耦合器输出信号相位差的新算法

本文提出了一种基于Bessel函数展开,在频域内精确确定光纤传感器3×3耦合器输出信号相位差的算法。在Mach-Zehnder干涉仪原理的基础上,通过建立3~3耦合器输出信号的数学模型和利用耦合器输出光功率的Bessel展开,完成了算法的理论推导,并且在实验室中进行了声学实验。数据处理结果表明,该算法能够较精确地确定3×3耦合器输出信号的相位差,且相位差与调制频率无关,与理论相符。     

利用全光纤耦合环实现三路光纤激光器的相位锁定

利用三个2×2的光纤耦合器按一定规则联接成一个全光纤耦合环,该耦合环将三个独立的掺铒光纤激光器连成一个锁相阵列. 由于耦合环的引入,锁相阵列的整体损耗减小,且三个单元激光器之间可以进行有效的能量相互注入耦合,进而实现阵列的锁相输出. 实验中观察到的远场干涉图样和锁相前后的输出光谱均表明三路光纤激光器实现了相位锁定,当三路抽运源的功率均为100 mW时,获得了92 mW的稳定相干输出. 关键词： 光纤激光器 相干合成 光纤耦合器 相位锁定     

一种基于哈特曼传感器的角锥棱镜检测方法

在使用角锥棱镜前对其进行检测,选取误差较小的棱镜是一项关系到整个测量工作结果的重要任务。因此,提出一种用哈特曼波前传感器全面检测角锥棱镜角度误差和面形误差的技术方案,从理论上分析了哈特曼法的测量原理,深入研究了光经过角锥棱镜后的波面重建,给出了波面特征与角锥棱镜误差参量之间的关系。在试验中验证了这种方法的正确性和可行性。     

一种改进的2×2 SOI Mach-Zehnder热光开关

本文设计并制作了基于强限制多模干涉耦合器的2×2 SOI马赫-曾德热光开关.这种光开关采用了深刻蚀结构的多模干涉耦合器和输入/输出波导,较大地提高了干涉耦合器的性能并减少了连接耦合损耗.同时,在调制臂区域采用浅刻蚀结构,保持其单模调制状态.深刻蚀多模干涉耦合器具有优越的特性,在实验中测得不均衡度只有0.03 dB,插入损耗－0.6 dB.基于这种耦合器的新型热光开关,其插入损耗为－6.8 dB,其中包括光纤-波导耦合损耗－4.3 dB,开关时间为6.8 μs.     

Femtosecond pulse switching in a fiber coupler with third order dispersion and self-steepening effects

A numerical study of femtosecond pulse propagation and switching in a dual-core nonlinear directional coupler with the consideration of third order dispersion and self-steepening effects is reported. The Split Step Fourier Method (SSFM) is used to investigate the switching characteristics of nonlinear directional couplers. It is observed that the energy transfer from core to core is not affected by changing the input pulse shapes except super-Gaussian. While the normalized coupling co-efficient and the input peak power dominate the coupling characteristics, the effects of third order dispersion (TOD) and self-steepening (SS) are also reported.