Experimental investigation of nonlinear process based on cSHG/DFG in PPLN waveguide

Effects of second harmonic generation (SHG) and cascaded second harmonic generation/difference frequency generation(cSHG/DFG) based on the quasi-phase-matching (QPM) condition in periodically poled lithium niobate (PPLN) waveguide were investigated experimentally. SHG conversion efficiency of-13.6 dB and QPM bandwidth of 0.45 nm were achieved using a 16.1 dBm power of fundamental wave at 1550.4 nm. Using pulsed all-fiber passive mode locked laser and tunable continuous wave laser,cSHG/DFG effect utilized for optical sampling was observed. Conversion efficiencies were calculated, and 11.88 nm-wide QPM bandwidth was achieved through changing the wavelength of input signal. Conversion efficiency of cSHG/DFG effect increased linearly with the total injected power.     

基于时间感知注意力机制的混合编码网络方法

传统的混合编码网络在小样本数据训练情况下,捕捉用户意图与语义分析方面存在局限性,很难应用到新领域进行迁移训练。时间感知注意混合编码网络(time-aware attention hybrid code networks,TAA-HCN)通过构建时间感知的注意力机制和用户意图集成(user intent integration,UII)的门控机制建模用户意图与动作措施的关系,捕捉用户意图随时间动态变化,结合元学习的思想进行模型梯度自适应,以便模型快速收敛。TAA-HCN模型在WOZ数据集与BABI数据集上进行试验与分析,当目标域数据为总数据的5%时,F1与BLEU指标几乎全收敛,且准确率为69.3%,这表明了本研究的模型具有仅需很少的目标数据即可实现良好性能的能力。     

用于波分复用的1×4多模干涉耦合器

根据多模干涉(MMI)技术和波分复用原理,设计并研制出应用于波分复用系统的1×4钛扩散铌酸锂(Ti:LiNbO3/LiNbO3)多模干涉耦合器.对MMI耦合器进行了理论研究和设计计算,完成了结构参数的优化设计、特性参数(损耗,分光比)的计算和实验验证,并与常规的M-Z型耦合器进行了对比.设计出的1×4MMI耦合器的长度为6 mm,损耗为1.4 dB,而使用三个M-Z型耦合器构成1×4耦合器,总长度为60 mm,总损耗为1.5 dB;因此,采用MMI耦合器,具有结构紧凑、损耗低、工艺简单、容差性好等一系列独特的优点.     

78fs全光纤环形腔被动锁模飞秒激光器

为满足全光采样系统对低时域抖动、窄脉冲宽度和高重复频率飞秒光纤激光器的需求,结合数值仿真,在实验的基础上利用非线性偏振旋转锁模原理,初步实现了自由运转被动锁模掺铒飞秒光纤激光器,激光器锁模输出脉冲的基本重复频率为6.028 MHz,平均输出功率为1.07mW,中心波长为l 570.3 nm,光谱宽度为33.2 nm,理...     

光弹效应法测定保偏光纤快慢轴

利用光弹效应原理深入研究了施加外力对保偏光纤的影响,并设计研制了保偏光纤快慢轴测试系统,其独特的高精度角度微调机构可以使保偏光纤快慢轴的测试精度达到±0.125°.最后用该测试系统对熊猫型保偏光纤进行了实验,输出光功率测量平均误差约为0.002 35 mW.     

Performance of Optical Sampling Based on SHG in CPPLN Waveguide

Sampling efficiency and bandwidth of the optical sampling system based on second harmonic generation (SHG) in chirped periodically poled LiNbO3 (CPPLN) are numerically researched. A broad sampling bandwidth can be obtained by adjusting chirp coefficient and waveguide length of CPPLN,and sampling efficiency can be improved by using higher pump power,increasing waveguide length and choosing appropriate chirp coefficient. Results show that both sampling bandwidth and efficiency in CPPLN waveguides are controll...     

海底管道缺陷在线智能检测机器人

分析了用MFL法检测管道缺陷时缺陷漏磁信号分辨率的特征,设计计算机控制的管道漏磁场分布测试系统检测、分析管道内漏磁场,优化设计用于小管径、厚管壁海底管道(ф273×12.7)缺陷检测的磁铁节,在此基础上设计制造了海底管道缺陷在线智能检测机器人,实验验证了机器人对人工模拟缺陷的检测能力.