微机电系统（MEMS） 垂直腔面发射激光器（VCSELs）是一种特殊光源，具有低功耗、高调制速率、宽波长调谐范围、易耦合等优点，被广泛应用于激光通信领域。为提升激光器工作性能，如扩大波长调谐范围、提高偏振对比度等，需要优化内腔亚波长光栅结构参数来改善腔内光场分布以及偏振输出模式。基于等效介质理论（EMT），并结合薄膜理论设计了针对调谐范围中心波长为850 nm、GaAs材料的亚波长光栅的较优周期、占空比、脊高的取值。分析了横电（TE）、横磁（TM）光，占空比与脊高对光栅透射率的影响。另外，通过系统模拟，对比了未刻蚀光栅、光栅未优化及光栅优化后的激光器波长调谐范围，结果表明：针对特定波长调谐范围及光栅材料，通过优化光栅参数可实现光栅对TE或TM光的增透，增强半导体腔和空气隙之间光场的耦合，进而扩大激光器的波长调谐范围。

As a type of special light source, microelectronic mechanical system (MEMS) vertical cavity surface emitting laser (VCSELs) has the advantages such as low power consumption, high modulation speed, broad wavelength tuning range and easy coupling, which has been widely applied in the field of laser communication. To achieve better performance of the lasers, such as enlarging wavelength tuning range and increasing polarization contrast, optimizing the structure parameters of inter cavity subwavelength grating is indispensable to improve the distribution of optical field and polarization output mode. In this paper, based on effective medium theory (EMT), the optimal values of period, duty cycle and ridge height of subwavelength grating are designed combining with the theory of film (the center wavelength of tunable range is 850 nm and the grating material is GaAs). The impact of grating duty cycle, ridge height on the transmission efficiency for TE and TM are analyzed. Furthermore, the tuning ranges of MEMS VCSELs with no-etched grating, unoptimized grating and optimized grating are compared. The results indicate that, for the specific wavelength tuning range and grating material, optimization of the grating parameters can promote the increase of the grating transmission efficiency for TE or TM mode, enhance the coupling of optical field between the semiconductor cavity and air gap, thus enlarge the wavelength tuning range of the laser.