Cut-off wavelength manipulation of pixel-level plasmonic microcavity for long wavelength infrared detection

The cut-off wavelength is one of the most important indicators for infrared detectors, and the manipulation of the cut-off wavelength is always an important demand in the application of long wavelength infrared detection. Traditional approaches to the cut-off wavelength extension would inevitably change the electronic states of the devices and lead to a large increase in the dark current, which usually causes performance degradations. Here, we demonstrate an optical method of the cut-off wavelength manipulation by plasmonic microcavities with the dark current being unchanged. We fabricate pixel-level devices with a single quantum well sandwiched in the microcavity and manipulate the cut-off wavelength from 14.3 to 16.3 μm while maintaining the peak responsivity higher than that of the standard 45° polished facet device. The experimental results are in good agreement with the numerical simulations, which indicates that the mechanism is mainly due to the properties of the dual mode manipulation in the plasm...