基于相位调制和光纤双折射光学倍频法

为实现毫米波信号的光学倍频法产生,利用相位调制器和光纤梳状滤波器,构建了光学倍频系统.其中光纤梳状滤波器由起偏器、双折射光纤和检偏器组成.理论分析表明,在该倍频系统中,通过对梳状滤波器双折射延迟量的选择,可有效地抑制非期望的奇次(偶次)谐波成分;通过对调相指数的优化,可进一步提高期望谐波分量的比例.仿真结果说明,利用该...     

Modelling Neutral Hydrogen Discs of Spiral Galaxies

We present an analytical model of a neutral hydrogen disc in a spiral galaxy.The gas disc of the spiral galaxy is assumed to have an exponential surface density profile and to be ionized by the cosmic ultraviolet background.To compare with observations,we consider the disc position angle and inclination angle for a line of sight going through the galaxy disc,The HI column densities depend on the strength of ionizing field and disc position and inclination.The model was applied to NGC 3198 and the results were compared with observational data.The Hi disc profile at large disc radii can be tested by further HI observations using radio telescopes with a larger aperture than the present facilities.This HI disc model can be used to predict quasar absorption line systems by galaxy discs if quasar lines of sight go through the discs.     

可变波片构造等效线性可转波片的研究

利用四元数理论分析了可变延迟波片,并依此由可变延迟波片组合构造了等效可转线性半波片和四分之一波片.提出由可变延迟波片按可转波片控制算法设计偏振控制器,以避免可变延迟波片偏振控制器所需的复位重置过程.仿真结果显示,按此构想得到的四波片控制器,能把任意偏振态转换为固定线偏振输出,其光强波动小于1%,相移范围不超过2π,控制过程不需要附加复位操作,其相移变化平缓.