Sum Frequency Generation Based Infrared Up‐Conversion in Thick Gallium Selenide Integrated Silicon Hybrid Metasurfaces

Abstract Infrared (IR) up‐conversion from the 3 to 0.8 µm wavelength range is demonstrated using resonantly enhanced second‐order sum‐frequency generation (SFG) in hybrid metasurfaces comprising of thick gallium selenide (GaSe) integrated amorphous silicon metasurfaces. Silicon‐on‐quartz metasurface comprising asymmetric meta‐atoms is designed to support collective electric‐dipole (ED)‐like and quasi‐bound‐state‐in‐the‐continuum (quasi‐BIC) resonances at 3.06 and 3.34 µm wavelength, respectively. The optimal thickness of multilayer GaSe is determined to be ≈70 nm in order to maximize the far‐field radiated SFG. The choice of a thick optimized GaSe layer in this work is motivated by its lower refractive index when compared to the silicon structures, resulting in minimal change to the optical resonances and electric field profiles while increasing the nonlinear interaction volume and far‐field radiated SFG. Resonant SFG up‐conversion from the hybrid structures is demonstrated with resonant enhancement of 59‐ and 35‐times from the ED‐like and quasi‐BIC resonances. To the best of the knowledge, this is the first report of such resonant infrared up‐conversion from the mid‐IR to shorter near‐IR using hybrid metasurfaces. This work paves the path for realizing compact frequency conversion devices operating across widely separated wavelengths using emerging resonant photonic platforms for potential applications in infrared sensing and imaging.