1 浙江工业大学理学院，智能光电研究所，浙江 杭州 310023
2 山东大学激光与红外系统集成技术教育部重点实验室，山东 青岛 266237
针对传统混合区域振幅自由度（MRAF）算法衍射效率低、非信号区域有散斑等问题，提出一种改进的MRAF算法。该算法引入球面相位作为初始相位，使用动态振幅限制，利用基于全域振幅限制的迭代方案确定最佳Z值，并使用爬山邻域算法对得到的相位进行分段式迭代优化，从而改善了非信号区域由于完全无振幅限制有散斑的问题。具体地，在全区域振幅限制阶段所提算法确保了目标光斑的匹配性并可以抑制散斑效应，而在混合区域振幅限制阶段则减小了误差。通过在三角形上进行数值仿真，对最终获得的结果进行光学实验仿真，结果表明，改进后的MRAF算法有97.77%高的衍射效率和0.09%低的均方根误差，并且峰值背景比（PBR）由0.0079提高至2.0357，相比基础的MRAF算法，对目标区域外围的散斑抑制效果更好，具有更高的应用价值。
衍射光学元件 光束整形 迭代算法 衍射光学元件设计 微纳光学 光学学报
2023, 43(22): 2223002
Author Affiliations
Abstract
Key Laboratory of Intelligent Optical Sensing and Manipulation, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
With the increasing demand for space optical communication security, space chaotic optical communication has attracted a great amount of attention. Compared with traditional space optical communication, a chaotic optical communication system has a higher bit error rate (BER) for its complex system design. In order to decrease the BER of space chaotic optical communication systems, we introduce two diffractive optical elements (DOEs) at a transmitting terminal (Tx). That is because the commonly used reflective optical antenna at Tx blocks the central part of the transmission beam, which leads to a great amount of power consumption. Introducing the DOEs into the optical subsystem at Tx can reshape the transmission beam from a Gaussian distribution to a hollow Gaussian distribution so that the block of the secondary mirror in the reflective optical antenna can be avoided. In terms of the DOE influence on communication quality, we give a BER model based on a minimum-shift-key (MSK) space uplink chaotic optical communication system to describe the DOE function. Based on the model, we further investigate the effect of the DOEs through analyzing the BER relationship versus basic system parameters based on the BER model. Both different mismatch conditions of chaotic systems and different atmospheric turbulence conditions are considered. These results will be helpful for the scheme design of space uplink chaotic optical communication systems.
chaotic-encrypted communication space uplink optical communication atmospheric turbulence effects diffractive optical element design minimum-shift-key bit error rate Chinese Optics Letters
2020, 18(7): 070601
1 中国科学院上海光学精密机械研究所, 上海 201800
2 中国科学院大学, 北京 100049
深紫外(DUV)光刻机照明系统普遍采用衍射光学元件(DOE)实现光瞳整形。根据光刻机的指标要求，衍射光学元件应具有高衍射效率和高均匀性的特点。传统的相位恢复算法如Gerchberg-Saxton (GS)及其改进算法，一般只能通过降低均匀性来提高衍射效率，无法得到最优的解。而全局优化算法如模拟退火法、遗传基因法等需要大量的计算时间，难以实现像素数目多的深紫外DOE 的设计。为了克服上述困难，提出了一种基于GS的混合梯度下降算法，在迭代过程中对每次迭代的振幅进行加权反馈修正，在加快收敛速度的同时，减少误差，同时实现高效率和高信噪比。利用该算法对光刻需要的传统、四极照明光瞳、定制照明光瞳的DOE 进行了设计，结果表明，实现传统和四极照明光瞳的16阶量化相位DOE 的衍射效率均超过92%, 而非均匀性分别为3.98%和2.3%。实现定制照明光瞳的DOE 的衍射效率为91%，图形恢复误差为5.8%。该方法为获得高性能深紫外DOE 提供一条可行的途径。
光学设计 光学光刻 光瞳整形 衍射光学元件设计 部分相干光
