Visible light metasurface for adaptive photodetection

Abstract

Semiconductor-based sub-wavelength metasurfaces are promising device platforms for the realization of optically thick and electrically thin photodetectors. Strong light–matter interactions in ultrathin film regions provide an opportunity to achieve near-unity absorption in dimensions comparable with carrier diffusion length and this, in turn, leads to an efficient collection of photogenerated carriers. Moreover, the use of phase change materials can provide real-time active tuning of optical responses of metasurface-based devices. In the first part of this paper, a tunable color filtering device is demonstrated using a metasurface design made of sub-wavelength antimony trisulphide (Sb2S3) grating placed on top of a continuous silver layer. Four distinct optical states can be acquired upon (a) the changes in the incident light polarization and (b) the phase transitions of Sb2S3. Numerical simulations and theoretical modeling data show that Fabry–Perot resonances are the driving phenomena when the proposed design is normally illuminated by an electromagnetic field with transverse electric polarization. In contrast, surface plasmon resonances are excited in transverse magnetic polarization. Furthermore, it is shown that the resonance wavelengths of the proposed design can be dynamically tuned using the geometrical parameters. Later, in the second part of the paper, adaptive photodetection is designed by integrating a $5\,$ nm Sb2S3 layer as a collection layer into the structure. The proposed metasurface design provides light–matter interaction in the Sb2S3 layer and maximizes the photogenerated carriers' collection efficiency. The optically thick and electrically thin adaptive photodetection offers an opportunity to design efficient active optoelectronic and photonic devices.