Wavelength-Agnostic Metasurface Design for Next-Generation 2D Photodetectors

We explore a versatile technique for inverse designing 2D photonic crystal metasurfaces. These surfaces, known for their ability to manipulate light-matter interactions, can be precisely controlled to achieve specific functionalities. The key lies in efficiently optimizing the geometric patterns and dimensions of the metasurface. Through a composite method which exploits two well-established paradigms - Covariance Matrix Adaptation optimization and Rigorous Coupled Wave Analysis (RCWA), we demonstrate our ability to design and optimize resonances in metaelements to achieve desired optical performance such as near-perfect absorption at chosen wavelengths/optical modes, which otherwise proves to be challenging or even impossible with conventional inverse design implementations. We apply our method to design three-layered structures involving a monolayer absorber, transparent metasubstrate, and a back mirror to get near 100% absorption at one or two chosen wavelengths. For illustration, we choose black phosphorus and silicon metasurface to predict ~100% absorption in a monolayer at 1550 nm. The versatile technique can be applied to tailor reflectance and transmittance for any optical mode and wavelength. This computationally efficient design method paves the way for creating high-performance 2D metasurface-based devices with a variety of applications, including quantum technology components such as single photon sensors and biphoton sources, communication systems, and non-linear light conversion.