有限口径非周期亚波长衍射聚焦偏转器的严格矢量优化

有限口径非周期亚波长衍射光学器件的亚波长结构特性使得传统标量衍射理论失效,必须借助严格电磁理论进行器件的设计。提出一种循环平面波谱算法(IterativePlaneWaveSpectrumAlgorithm,IPWSA)作为器件优化算法,利用二维时域有限差分方法作为严格电磁计算模式,根据Farn方法对器件面型进行亚波长处理,设计出有限口径非周期具有亚波长结构的衍射聚焦偏转器件,偏转角为24.8°,该器件可与激光器集成构成微型集成光学系统,也可以用在红外量子阱系统中。详细分析了算法原理,设计实例验证了算法的优化效果。

Vector-based optimization of finite aperiodic diffractive focusing deflector with subwavelength structures

An iterative vector-based optimization algorithm is presented for the design of diffractive optical elements (DOEs) with subwavelength structures as a beam focusing deflector. The DOEs with subwavelength structures, have the ability for monolithic integration and can require only single step fabrication, but the subwavelength and aperiodic nature of the DOEs prevent the use of scalar diffraction theory and the use of coupled-wave theory. The finite-difference time-domain (FDTD) method as the electromagnetic computational model and the iterative plane wave spectrum algorithm (IPWSA) as the optimization algorithm, which can make the design of DOEs in reasonable time frames,have been applied for designing DOEs. The IPWSA, the FDTD method, the plane wave spectrum propagation method and the Farn method are discussed. By using the iterative algorithm, a beam deflector with subwavelengh structures was designed for normal incidence TE mode illumination, which has shown that the optimization algorithm is valid and competent for rigorously designing diffractive optical elements.