Opt Express. 2023 May 8;31(10):16025-16034. doi: 10.1364/OE.487119.
We demonstrate monolithic high contrast gratings (MHCG) based on GaSb/AlAsSb epitaxial structures with sub-wavelength gratings enabling high reflection of unpolarized mid-infrared radiation at the wavelength range from 2.5 to 5 µm. We study the reflectivity wavelength dependence of MHCGs with ridge widths ranging from 220 to 984 nm and fixed 2.6 µm grating period and demonstrate that peak reflectivity of above 0.7 can be shifted from 3.0 to 4.3 µm for ridge widths from 220 to 984 nm, respectively. Maximum reflectivity of up to 0.9 at 4 µm can be achieved. The experiments are in good agreement with numerical simulations, confirming high process flexibility in terms of peak reflectivity and wavelength selection. MHCGs have hitherto been regarded as mirrors enabling high reflection of selected light polarization. With this work, we show that thoughtfully designed MHCG yields high reflectivity for both orthogonal polarizations simultaneously. Our experiment demonstrates that MHCGs are promising candidates to replace conventional mirrors like distributed Bragg reflectors to realize resonator based optical and optoelectronic devices such as resonant cavity enhanced light emitting diodes and resonant cavity enhanced photodetectors in the mid-infrared spectral region, for which epitaxial growth of distributed Bragg reflectors is challenging.
我们展示了基于 GaSb/AlAsSb 外延结构的整体高对比度光栅 (MHCG)，其亚波长光栅能够实现 2.5 至 5 µm 波长范围内非偏振中红外辐射的高反射。我们研究了脊宽从 220 到 984 nm 且固定 2.6 µm 光栅周期的 MHCG 的反射率波长依赖性，并证明了对于脊宽从 220 到 984 nm 的情况，峰值反射率可以从 3.0 µm 分别移动到 4.3 µm。在 4 µm 处可以实现高达 0.9 的最大反射率。实验与数值模拟吻合良好，证实了在峰值反射率和波长选择方面具有很高的工艺灵活性。MHCG 一直被认为是能够实现所选光偏振高反射的镜子。通过这项工作，我们表明经过深思熟虑设计的 MHCG 能够同时实现对两个正交偏振的高反射。我们的实验表明，MHCG 是替代传统镜子（如分布式布拉格反射镜）的有前途的候选者，可用于在中红外光谱区域实现基于谐振腔的光学和光电设备，例如共振腔增强发光二极管和共振腔增强光电探测器，对于后者，分布式布拉格反射镜的外延生长具有挑战性。
