AlSb as a material for high index contrast nanophotonics

Abstract

High contrast materials, i.e., materials with a high refractive index and low optical loss, are of wide interest for nanophotonics and metasurface designs at optical and near infrared wavelengths. We explore aluminum antimonide (AlSb) as a high contrast nanophotonic material, using the design of high contrast gratings (HCGs) for low loss dielectric mirrors as an example. The high index of refraction and low absorption coefficient of AlSb in the visible wavelength range enable designs of HCGs that can be effectively optimized to form mirrors with 93.5% reflectivity at red visible wavelengths. We detail a co-sputtering synthesis method for AlSb films, and achieve our target high index of refraction of 3.5 for 635 nm light. We also find that the high sensitivity of AlSb oxidation requires specific handling procedures in developing deposition processes to yield a near zero absorption coefficient.