用于激光阵列发生器的非n×n型Danmmann光栅研制

Fabrication and Characterization of Non-n×n Dammann Grating for Spot-Array Generator

为实现激光阵列发生器点阵列任意排布,研制了一种非n×n型达曼(Danmmann)光栅。本文以严格耦合波分析理论为基础,设计了一种衍射效率较高的4台阶非n×n型Dammann光栅,采用快速傅里叶变换算法进行了优化。运用Virtual Lab仿真软件进行模拟,形成两行强度均匀的点光斑,排布方式为第一行为4个,第二行为3个,总衍射效率为93.30%,不均匀性小于5%。通过电子束光刻直写进行变剂量曝光制作抗蚀剂掩模,并采用反应离子刻蚀技术以石英为基底制作出了非n×n型Danmmann光栅。通过扫描电子显微镜测得了光栅面型,并分析了光栅表面粗糙度,根据反应离子刻蚀过程中射频功率、工作气压及气体流量3种工艺参数对表面粗糙度的影响程度,确定光栅了制备工艺的最优参数组合。结果表明:当射频功率为110 W,工作气压为1×10^(-3)Pa,气体流量为35 m L/min时,光栅的表面粗糙度值最佳,值为23.45 nm。

A novel type of highdiffraction-efficiency,non-Dammann grating with 4-step structure,was designed based on Rigorous Coupled-Wave Analysis （RCWA）, optimized by fast fourier transform （FFT） algorithm, fabrica- ted by electron-beam lithography and reactive ion etching, numerically simulated with software VirtualLab, and ex- perimentally tested, to generate an array of arbitrarily distributed laser spots. The simulated results show that the novel grating array, consisting of the four-spot 1st-line and three-spot 2nd - line, has a diffraction efficiency over 93.30% ,and a non-uniformity below 5%. The impact of the fabrication conditions, including The RF power,flow- rate of CHF3. and pressure on the surface roughness of the grating was investigated with scanning electron microsco- py. The experimental results show that the newly-developed Dammann grating with surface roughness of 23.45 nm was fabricated under the optimized conditions： a RF power of 110 W, a pressure of 10^-3 Pa and a CHF3 flow-rate of 35 mL/min