Low-loss switchable metasurface-based waveplate using phase change of antimony triselenide for telecom applications

In this paper we introduce the design of a switchable metasurface waveplate using low-loss phase-change material. The structure includes Antimony Triselenide grating deposited over a glass substrate, which can be easily fabricated using standard silicon fabrication technology. By employing the different birefringent effect induced, the grating operates as a quarter-wave plate when Antimony Triselenide is in the amorphous state, and operates as a half-wave plate when it is in the crystalline state. The grating parameters (thickness, height, and period) are optimized using global genetic algorithm. The design provides above 80% transmission for amorphous and crystalline states over the telecom band between 1.3 and 1.65 μm. The proposed design constitutes an important device for integrated silicon nanophotonics and flat optics applications.