High-efficiency subwavelength bridge-shaped photo-absorbers based on transverse cavity modes

We study a frequency-selective photon absorber able to efficiently confine light within very thin semiconducting layers. The active material is appropriately embedded in a cavity resonator where lateral resonances occur, based on nonplasmonic modes, thus minimizing undesired losses in the metallic parts. Typical examples and configurations in the infrared and visible ranges are illustrated. Theoretical quantum efficiencies around 90% may be reached, with a broad angular tolerance. Also, multispectral photon sorters may be designed by combining resonators of different sizes. These results especially find direct applications for elementary ultracompact detectors and imaging focal plane arrays.