Design of midinfrared photodetectors enhanced by resonant cavities with subwavelength metallic gratings

We propose a metallic Fabry–Pérot cavity with a Au grating and a Au film acting as two reflectors to enhance the field and absorption in the active detector region, leading to better performance of quantum-dot-based photodetectors at a wavelength of 10 μm. One- and two-dimensional Au gratings are applied to achieve enhancement for polarized and unpolarized light, respectively. With optimizing grating parameters, the absorption can be enhanced by about 20 times in the active detector region compared to conventional photodetectors without the Au reflectors.