The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adom.201901800.Circularly polarized light (CPL) has its electric field rotating with a constant magnitude in a plane perpendicular to the direction of the wave. Based on the direction of rotation, a circularly polarized wave is either left-circularly polarized (LCP) or right-circularly polarized (RCP), corresponding to the two spin states of photons. Owing to the superior robustness of circular polarization states during transmission, [1] during asymmetrical interaction with chiral matters, [2] and in the quantum information carried by its photon spin states, [3] circularly polarized light has promising applications in optical communication, [4] imaging, [5] sensing, [6] and quantum information processing. [7][8][9] Adv. Optical

for S m = 5 μm × 5 μm or S m = 10 μm × 10 μm. Further, the meta-lens exhibits a good dispersion tolerance over the wavelength range from 3.3 μm to 5 μm. The averaged detectivity enhancement over this spectrum range is around 3 times for S m = 5 μm × 5 μm and 2 times for S m = 10 μm × 10 μm. The angular response of the meta-lens integrated detector depends on the focal length. For a focal length of 73 μm, the AOV for a 5 μm × 5 μm photosensitive area is 4.0°. When the focal length is reduced to 38 μm, the AOV for a 5 μm × 5 μm photosensitive area increases to 7.7° and it reaches 15.4° for a 10 μm × 10 μm photosensitive area. For the inter-pillar distance to be 2 μm in our design, the influence of the coupling effect between the nano-pillars on the performance of the meta-lens is little. Therefore, the monolithic integration of a meta-lens provides us a promising way to enhance the performance of infrared photodetectors and even focal plane arrays.

Multi-resonance light coupling management is a promising way to expand the operating spectral ranges of optoelectronic devices. The classical strategies are either lack of independent tunability for each resonance or involved with complex fabrication. Here, we propose a new scheme for expanding the operating spectral range of an optoelectronic device through a dual-color active material integrated with a simple resonant waveguide structure. The TM waveguide mode and the SPP mode of the resonant waveguide structure are regulated to match the two active regions of the dual-color material both spectrally and spatially. Applying this scheme to a long-wavelength infrared quantum well photodetector, the absorption efficiencies at the two peak detection wavelengths of the dual-color quantum wells are both enhanced by more than 10 times compared with the case of a standard 45° edge facet coupled device with the same detection material. The simple light coupling structure is easy to accomplish and compatible with focal plane arrays. For thermal radiation detection, the absorption efficiency of the 300 K blackbody radiation by our dual-color detector is 83.8% higher than that by a single-color detector with the optimized structural parameters. Moreover, either polarization sensitive or polarization insensitive detection could be achieved in this dual-color infrared quantum well photodetector by using anisotropic or isotropic gratings.

The light coupling properties of all-semiconductor plasmonic cavity integrated THz quantum well infrared photodetectors were studied for absorption enhancement of the quantum wells. The all-semiconductor plasmonic cavity is constructed by heavily doped GaAs with a plasmonic behavior in the THz regime. The plasmonic behavior of GaAs was thoroughly studied by taking into account the carrier density dependent effective mass of electrons. An optimal doping level for GaAs to be the most metallic is selected since the plasma frequency of the doped GaAs varies nonmonotonically with the carrier density. By tuning the absorption competition between the quantum wells and the doped GaAs meanwhile keeping the system at a critical coupling status, the absorptance of the quantum wells is prominently enhanced by 13.2 times compared to that in a standard device. The all-semiconductor plasmonic cavity integrated quantum well photodetectors can be polarization sensitive (polarization extinction ratio > 900) when the plasmonic cavity is shaped into an anisotropic form. The good tolerance of the incident angle is favored for wide-field infrared detection. The GaAs plasmonic cavities are demonstrated to be effective when integrated at a pixel level, indicating a good compatibility with focal plane arrays.