2D Material Based Nonlinear Optical Mirror for Widefield Up-Conversion Imaging from Near Infrared to Visible Wavelengths

Abstract

Infrared up-conversion imaging is used for frequency conversion of near and mid-infrared photons to the visible or shorter near-infrared wavelength range where high-performance silicon sensors can be used for imaging in-lieu of the cumbersome infrared counterparts. Nonlinear optical crystals are used for up-conversion imaging, however, this typically requires long lengths, high pump power, and careful phase matching between interacting waves. To miniaturize the up-conversion imaging device and eliminate stringent phase-matching requirements, sub-wavelength size optical metasurfaces are being explored as the nonlinear optical medium supporting resonances in the near-infrared, albeit being prone to higher-order diffraction at the up-converted wavelengths. Here, a novel two-dimensional (2D) layered material-based nonlinear optical mirror (NLOM) based wide-field up-conversion imaging device is demonstrated with only 45 nm thick Gallium Selenide (GaSe) layer on a gold reflector with a suitable dielectric spacer. Near-infrared input at 1550 nm is up-converted to 622 nm visible output in the presence of a pump beam at 1040 nm through a sum frequency generation (SFG) process. The NLOM stack is optimized using particle swarm optimization algorithm for maximizing the detected SFG signal. Image up-conversion experiments are performed demonstrating real, Fourier-plane imaging, and real-time Fourier-domain processing with good imaging fidelity and efficiency.