基于微结构演化的V5Cr5Ti合金塑性本构模型

为合理描述V5Cr5Ti合金的塑性变形行为，本文建立了基于微结构演化的塑性本构模型。首先，采用小尺寸试样开展了V5Cr5Ti合金单轴拉伸试验，并对其在不同应变程度下的微结构演化特征进行了分析。研究发现，影响V5Cr5Ti合金塑性变形行为的主要因素是位错密度演化以及团簇状和弥散析出相。据此建立了位错密度演化方程、组分相含量体积分量演化方程，并考虑团簇状和弥散状第二相对V5Cr5Ti合金流动应力的影响，进一步建立了包括非热应力、热激活应力和弥散相强化应力的流动应力关系式。最后，根据隐式应力更新算法对新模型进行了有限元实现，并与实验结果进行比较，验证了新模型的合理性和预测精度。     

High power pulse amplification of ytterbium-doped double-clad fiber amplifier

By solving a set of time-dependent equations,the characteristics of the ytterbium-doped double-clad fiber amplifier are presented.Besides the steady state in the fiber of the upper-state population,pump power and amplified spontaneous emission without the input signal,the dynamic characteristics of the high power Gaussian pulse amplification like the evolution of pulse waveform distortion,upper-state population distribution and stored energy and pulse energy of the amplifier under the forward and backward pump, are simulated.The relations between the output pulse energy of the amplifier and the different input pulse peak power or pump power are also discussed.The models and results can provide important guide for the design and optimization of the high power pulse amplification.     

Single Mode Er-Doped π-Phase-Shifted Distributed Feedback Fibre Grating Laser

A novel method incorporating the shielded method and the post-processing method has been proposed to fabricate the π-phase-shifted fibre grating. Then an Er-doped π-phase-shifted distributed feedback fibre grating laser has been fabricated using the grating. The laser threshold is 20mW. When pumped with 90mW light at 980nm, the laser gives an output of 1.1mW. Its signal-to-noise ratio is better than 60dB. It is demonstrated that the laser is single mode operation by means of a Fabry--Perot scanning interferometer.     

掺Yb光纤激光器激射波长与阈值关系研究

依据石英中 Yb3 的能级和光谱特性 ,推导了掺 Yb光纤激光器中激射波长与抽运阈值等的关系式。依据所得到的关系式 ,深入分析、研究了抽运功率、损耗及阈值对激光运行波长的影响。进行了相关实验 ,理论与实验结果符合得很好     

掺Yb双包层光纤激光器波长调谐输出

采用调节腔损耗以调节阈值的方法实现了掺Yb双包层石英光纤激光器的波长调谐输出 调谐范围达50nm 、步长约2nm 当损耗增大阈值升高时,激射波长向短波方向漂移.利用石英中Yb³⁺的能级结构和光谱特性对以上规律进行了定性解释.     

一种利用相位掩模版对光栅波长进行微调的光栅刻写方法

提出并实验证实了一种刻写光栅时既能保护相位版又能对光栅的反射波长进行微调的方法.通过调整光纤和相位版之间的距离,利用1 550 nm单模光纤和掺铒分别实现了0.48 nm和2.2 nm的光栅反射波长的调节.在相位版和光纤之间的距离保持在3 mm的条件下,既可以保护相位版又可以获得高质量的光栅.     

激光共振喇曼光谱和血—气分析研究血红蛋白的氧合与脱氧

两条特征喇曼谱带ν(Fe—O_2)=572cm~(-1)和ν(=C—N)=1387cm~(-1),1392cm~(-1)可以作为探针研究血红蛋白组份的氧合与脱氧机制。我们对分离了的血红蛋白组份Hb—A和Hb—F测定了它们的喇曼谱带光强Ⅰ1392cm~(-1)和氧分压Po_2的曲线。同时,用IL813型和282型血-气分析仪测量了正常成人血(含Hb—A 97%)和脐带血(含Hb—F 80%)的氧解离曲线。实验中听得到的两条曲线的形状和趋势很相似。它们可以从血红蛋白的氧合与脱氧机制上解释正常成人、胎儿、新生婴儿和血液病患者的某些生理和病理现象。     

Yb3+相移分布反馈光纤激光器的理论分析

对相移分布反馈掺Yb^3 光纤激光器进行了理论分析，发现当相移为π时，增益阈值最小，相移越远离π，增益阈值越大，信号波长越偏离布拉格波长；随着光纤光栅耦合系数的增加，激光器的增益阈值越小，输出功率越大；相移分布反馈光纤激光器的正向和反向输出持性与光纤光栅的相移点的位置有关。     

影响相移光纤分布反馈激光器的增益阈值的因素

本文从理论上分析了在光纤光栅的调制度一样的情况下,影响光纤分布反馈激光器的增益阈值的几个因素:相移量的大小,相移区的长度以及相移区在光纤光栅中的位置.     

Theoretical modelling of the effect of photon lifetime on the output dynamics of Er-doped distributed feedback fibre lasers

By employing a simple model of describing three-level lasers, we have theoretically investigated the effect of photon lifetime on the output dynamics of Er-doped distributed feedback fibre lasers. And based on the theoretical analysis we have proposed a promising method to suppress self-pulsing behaviour in the fibre lasers.