快速响应的硅基纯相位液晶器件对动态大气湍流波前的校正能力研究

Dynamic wavefront correction with a fast liquid-crystal on silicon device of pure phase

液晶相位调制器的响应时间延迟是影响液晶自适应光学系统性能的一个主要因素,为了提高系统的响应速度,开发了一种快速响应的向列相液晶材料,并制成了反射式硅基液晶器件(LCOS).分析了该LCOS的相位调制特性及其对静态畸变波前和扰动波前的校正能力.首先,测量了LCOS的电光响应特性,得出其780 nm相位调制量的响应时间为2 ms.其次,测量了LCOS的相位调制特性,并对相位调制进行了线性化处理.再次,测量了用该LCOS搭建的液晶自适应光学系统的闭环和开环3 dB带宽,它们分别为16和18 Hz.最后,给出了开环液晶自适应光学系统校正大气湍流的数值模拟结果,结果表明.系统的Strehl比由校正前的0.025上升到了校正后的0.225.因此,该液晶自适应光学系统可以对Greenwood频率为30 Hz以下的大气湍流进行较良好的校正.

In order to increase the response speed of the liquid crystal phase modulator （LCPM）, a new kind of fast liquid crystal material is designed and synthesized, and a corresponding LCPM, called liquid crystal on silicon （LCOS）, is fabricated. We test the phase modulation of the LCOS and exanxine its wavefront correction ability on static and disturbed wavefront. First, the electro-optical response is tested. The response time to a phase modulation quantity of 780 nm is 2 ms. Second, the phase modulation of the LCOS is tested and linearized. Third, the 3 dB closed-loop and open-loop disturbance rejection bandwidths of the adaptive optics system （AOS） are measured to be 16 and 18 Hz, respectively. Finally, the simulated correction of 26 Hz turbulence with the open-loop AOS is conducted. After correction, the Strehl ratio increases from 0.026 to 0.225. Therefore, with our fabricated LCOS, the liquid crystal AOS is able to correct the turbulence below 30 Hz.