设计了一种用于850 nm GaAs基VCSEL的高折射率对比度亚波长光栅（HCG），整体结构采用GaAs材料体系，包含光栅层及为缓解其应力问题而设计的应力缓冲层和以AlGaAs或AlAs氧化后形成的AlO_x低折射率亚层。通过Rsoft软件对HCG的反射特性进行仿真研究，分析了不同光栅参数对反射谱的作用规律，重点探究了应力缓冲层和低折射率亚层对光栅特性的影响。设计了中心波长850 nm 的TM模HCG，反射率大于99.9%的带宽可达91 nm，与中心波长之比达到10.7%，同时TE模的反射率不超过90%，显示出了良好的偏振选择性。该结构可以替代VCSEL中的P型分布式布拉格反射镜，提供高反射率、宽带宽，并改善由不同材料体系所导致的应力问题，提高器件稳定性。

A high-refractive-index contrast subwavelength grating （HCG） for 850 nm GaAs-based VCSELs was designed. The whole structure is based on GaAs material system，including a grating layer， a stress buffer layer designed to alleviate its stress problem and an AlO_x low refractive index sub-layer oxidized by AlGaAs or AlAs. The reflection characteristics of the HCG are simulated by Rsoft software， and the effects of different grating parameters on reflection spectrum are analyzed. In particular， the effects of stress buffer layer and low refractive index sub-layer on characteristics of gratings are investigated. The 850 nm TM mode HCG shows a very good reflection characteristic. It has a large reflection bandwidth of up to 91 nm with its reflectivity more than 99.9%， and the ratio with the center wavelength reaches 10.7%. Moreover， its reflectivity for TE mode is ensured to be lower than 90%， showing good polarization selectivity. This HCG can replace P-type distributed Bragg reflectors in VCSEL， providing high reflectivity， wide bandwidth， and good stability.