基于亚波长光栅的VCSEL偏振控制研究

为了确定亚波长光栅在微电机械系统(MEMS)波长可调谐VCSEL不同位置(上DBR上表面、上DBR下表面以及内腔)中实现TE和TM偏振控制的光栅参数范围以及光栅在哪个位置时实现偏振控制最稳定,通过MATLAB建立MEMS波长可调VCSEL的模型,然后计算光栅在3种位置时上反射镜(包括空气隙和光栅)随光栅参数变化的反射率,以此来确定它们实现TE/TM稳定偏振的光栅参数范围(即高反射范围内的参数)。将各自的高反射所对应反射率减去相同光栅参数范围内TM/TE低反射对应的反射率,通过反射率差值确定光栅在哪种位置时MEMS波长可调谐VCSEL实现偏振是最稳定的。最后得出的结论是光栅在上DBR下表面几乎无法控制TM偏振,而将光栅放置于内腔中,无论是在TE偏振控制上还是TM偏振上都是最稳定的。在实现TE偏振稳定的参数范围内,TE的阈值增益比TM最小少10 cm~(-1);而在实现TM偏振稳定时,在TE偏振稳定的参数范围内,TE的阈值增益比TM最小少5 cm~(-1)。

Polarization Research of VCSEL Based on Sub-wavelength Grating

In order to confirm the sub-wavelength grating parameters and the best position the sub-wavelength grating being placed in micro-electro-mechanical system (MEMS) wavelength tunable VCSEL(top DBR surface, top DBR bottom surface, inner cavity) range to realize stable polarization control, MATLAB was used to build MEMS wavelength tunable VCSEL model, then the reflectivity of three structures` top reflective mirror (top DBR, grating, air gap) changing with the sub-wavelength grating parameters were calculated by which the grating parameters range (high reflectivity) making TE/TM polarization of the three structures stable could be confirmed.The reflectivity difference for which the high reflective corresponding reflectivity minus the low reflective corresponding reflectivity in the same grating parameters range can determine the position where the sub-wavelength grating is placed to realize the most stable polarizations.The results show that the sub-wavelength grating on the bottom surface of the top DBR mostly can not control TM polarization, while not only TE polarization but also TM polarization is most stable when the grating is placed in the inner cavity.TE polarization threshold is less than TM polarization of 10 cm-1 within the grating parameters range to realize TE polarization stable, while TM polarization threshold is less than TE polarization of 5 cm-1 within the grating parameters range to realize TM polarization stable.