RESUMO
We present an imager architecture comprising dark and active pixels allowing the simultaneous measurement of photonic and dark current, which is of particular interest for low-photon-flux astronomical applications. The principle of operation relies on both the total opacity of a thin metallic screen of sufficient area and the anti-reflective properties of well-designed resonant metal-dielectric gratings made on the same screen. The concept is exemplified in the context of cooled HgCdTe hybrid detectors, at short- and long-wave infrared ranges.
RESUMO
Standing wave resonating cavities have been proposed in the past to increase the performance of infrared detectors by minimizing the volume of photogeneration, hence the noise, while maintaining the same quantum efficiency. We present an approach based on the temporal coupled mode theory to explain their behavior and limitations. If the ratio of the imaginary part of the absorber's dielectric function to the index of the incident medium εâ³(d)/n0 is larger than 1.4, then the absorption cross section σ(a) can attain its maximum value, which for an isolated cavity is approximately 2λ/π. Besides, for σ(a) to exceed the cavity width, the incident medium refractive index must be close to unity. Metallic loss is negligible in the infrared, making those resonators suitable for integration in infrared photodetectors.
RESUMO
We use numerical simulations to show that a suitably dimensioned periodic arrangement of vertical metallic metal-dielectric-metal nanocavities supports a hybrid plasmonic mode whose spatial electric field distribution is suitable for use in infrared photodetectors based on an unpatterned semiconductor thin-film absorbing layer. The partially localized nature of the hybrid mode offers reduced sensitivity to the angle of incoming light and smaller pixel sizes compared with surface plasmonic modes coupled by diffraction.
