采用折射率椭球基本理论和数值计算方法,分析了纵向和横向调制下,出射光光强随温度的变化趋势,以及在这过程中与晶体折射率、晶体热膨胀系数及晶体尺寸间的关系,并进行了相应的数值模拟。结果表明,纵向调制下出射光光强随温度的变化趋势只跟晶体折射率的变化有关;横向调制下出射光光强随温度的变化趋势不仅要受到晶体折射率的影响,还要受到晶体尺寸及其膨胀系数的影响,因此可以利用特殊尺寸的晶体来提高电光调制器的温度稳定性。

By using the basic theory of the refractive indices ellipsoid and numerical calculation, the relationships of the tendency of change of the emitted light intensity with temperature, with the crystal refractive index, the crystal size, and the crystal expansion coefficient respectively, under the transverse and longitudinal modulation were simulated, and then carried out the appropriate numeri-cal calculation. The results show that the tendency of change of the emitted light intensity with temperature under the longitudinal modulation only can be affected by crystal refractive index. Not only the crystal refractive index but also the crystal size and its expan-sion coefficient can affect the tendency of change of the emitted light intensity with temperature under the transverse modulation. So the temperature stability can be improved by using crystal in specific size to present an optimal design of electro-optic modulator.

利用Fluent软件,模拟计算了垂直Bridgman法大尺寸氟化钙晶体生长的具体过程,研究了晶体生长过程中的热传递和熔体对流传热,分析了固相、液相和坩埚的热导率的差异对坩埚中心轴的轴向温度分布和轴向温度梯度以及界面处的径向温度分布和径向温度梯度的影响。分析结果表明:熔体对流传热的效果随晶体生长的不断进行逐渐减弱;固相、液相和坩埚的热导率的差异对坩埚中心轴的轴向温度分布和轴向温度梯度以及界面处的径向温度分布和径向温度梯度有重要影响;晶体的结晶速度和坩埚的下降速度存在不一致性。

With Fluent software,specific growth process of large size calcium fluoride crystals by the vertical Bridg-man method was simulated and calculated. The heat transfer and the melt convection of crystal growth process were investigated. The difference of the thermal conductivity of solid phase,liquid phase and crucible has effect on axial temperature profile and axial temperature gradient profile along the centerline of the crucible and radial temperature profile and radial temperature gradient profile at the solid-liquid interface was analyzed. The results show that the effect of the melt convection heat transfer becomes weak with continuous crystal growth;The difference of the thermal conductivity of solid phase,liquid phase and crucible has important effect on axial temperature profile and axial tem-perature gradient profile along the centerline of the crucible and radial temperature profile and radial temperature gra-dient profile at the solid-liquid interface;Rate of crystallization

光子晶体光纤光栅是一种新型的无源器件,可广泛用于光纤通信系统、光脉冲压缩、传感器及滤波装置中.采用耦合模理论对光脉冲在光子晶体光纤光栅中传播进行分析,给出光子晶体光纤光栅的制作方案,提出了光子晶体光纤光栅在压力传感器、折射率传感器、应变传感器和射流传感器等方面的具体应用.光子晶体光纤光栅对温度的敏感性比传统单模光纤传感器要低2至3个数量级,光子晶体光纤光栅传感器系统不需要温度补偿,传感器系统更为简洁而具备充分的优越性.

As a new passive device, photonic crystal fiber grating can be widely used in optical fiber communication systems, optical pulse compression, sensors and filtering devices. With the coupled-mode theory, this paper analyzes the optical pulses propagation in photonic crystal fiber gratings, and the obtained methods of photonic crystal fiber gratings. It summarizes its applications in photonic crystal fiber grating pressure sensor, the refractive index sensors, strain sensors and the fluidic sensors. The temperature sensitivity of photonic crystal fiber grating is at lower 2-3 orders of magnitude than that of conventional single-mode fiber, photonic crystal fiber grating sensor does not need temperature compensation, so this sensors is more concise and sufficiently superior.

分别在室温(25℃)和高温(300℃)下,通过X射线衍射实验对Mg F2和Sr F2晶体进行了晶体结构的检测.利用基于Rietveld精修方法的RIETAN-2000程序对所得实验结果进行了解析,精修了Mg F2和Sr F2晶体在不同温度下的各晶体结构参数,获得了原子各向同性温度因子B.通过Maximum Entropy Method(MEM)解析得到了Mg F2和Sr F2晶体的等高电子密度分布图谱,实现了电子密度分布的可视化.

In this paper, the crystal structures of MgF2 and SrF2 were tested by X-ray diffraction ( XRD) at room temperature (25℃) and high temperature (300℃), respectively.The crystal structure parameters were refined and the temperature factor B was obtained with Rietvled method which was carried out in the RIETAN-2000 program.In addition, the XRD results were analyzed with Maximum Entropy Method ( MEM) method and the electron density distributions were shown clearly in the form of equal pitch contour, which realized the visual-ization of the distribution of electron density.

光子晶体光纤陀螺技术是解决光纤陀螺空间辐照及热漂移问题的重要技术途径,其中光子晶体光纤环是影响光纤陀螺性能的关键。仿真分析了光子晶体光纤的双折射与结构设计的关系,并计算了光纤的双折射和光纤环绕制过程引入的附加双折射的温度灵敏度,利用白光干涉仪,对光子晶体光纤环和普通的保偏光纤环进行了对比测试分析。试验结果表明,光子晶体光纤环具有较低的偏振特性温度灵敏度,双折射温度系数比普通保偏光纤低接近1个量级,引起的陀螺偏振误差也比普通保偏光纤环小1倍左右。试验结果验证了理论分析的正确性。

Photonic crystal fiber optical gyroscope(PC-FOG) is an important technical approach to overcome the influences of space irradiation and thermal effect on fiber-optic gyroscope. The fiber coil is an essential part of a FOG which affects the FOG’s performance in space environment. In this paper, the birefringence of photonic crystal fiber(PCF) coil was simulated and its temperature coefficient was calculated. Comparison tests were conducted to analyze the difference between PCF coil and polarization maintaining fiber(PMF) coil. The results indicate that the birefringence temperature coefficient of PCF coil is lower by one order of magnitude than that of PMF coil, and this tends to reduce the polarization error of FOG by one times. The experiment measurements demonstrate their good agreement with theoretical analyses.