Monolithic All-Silicon Flat Lens For Broadband Lwir Imaging

We designed, fabricated, and characterized a flat multi-level diffractive lens comprised of only silicon with diameter = 15.2 mm, focal length = 19 mm, numerical aperture of 0.371, and operating over the long-wave infrared (LWIR) spectrum = 8 mu m to 14 mu m. We experimentally demonstrated a field of view of 46 degrees, depth of focus >5 mm, and wavelength-averaged Strehl ratio of 0.46. All of these metrics were comparable to those of a conventional refractive lens. The active device thickness is only 8 mu m, and its weight (including the silicon substrate) is less than 0.2 g. (C) 2021 Optical Society of America