High circular polarization recognition quantum well infrared photodetector based on a chiral metamaterial microcavity

Circular polarization detection has important applications in the field of infrared detection. In this paper, a chiral metamaterial microcavity is designed to enhance the recognition of circularly polarized light (CPL) by a quantum well infrared photodetector (QWIP). By sandwiching the quantum well material and GaAs electrodes between a metallic chiral metamaterial and a gold substrate to form a microcavity structure, CPL discrimination can be achieved, and inter-subband absorption in the quantum well active region can also be improved. The electric field distribution is calculated and analyzed with the finite-difference time-domain method. Under the incidence of left circularly polarized light, the metallic chiral metamaterial on the surface excites the surface plasmon polariton (SPP) effect, which enhances the electric field (EZ) perpendicular to the growth direction of the quantumwell, and the coupling efficiency can reach 950% at 14.9 _mwavelength. The SPP resonance wavelength matches the inherent response wavelength of the quantum well, so the inter-subband absorption of the quantum well is increased to about 0.9. At right circularly polarized light incidence, the coupling efficiency is only 105%, and the inter-subband absorption is only about 0.1 because the SPP effect is not effectively excited. Since chiral metamaterials can enhance the circular dichroism of quantum wells, when our designed structure is combined withQWIP, the circular polarization extinction ratio of QWIP can be increased to nine, which is much higher than 2.5 for a typical circular polarization detector. In addition, the inter-subband absorption will also be greatly improved under the incidence of CPL in a specific rotation direction. By optimizing the structural parameters, the resonance wavelength can be matched with the QWIP of different detection bands, which provides a new idea for the improvement of the performance of a quantumwell infrared circular polarization photodetector in the long wave range.