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.
Highlights
High refractive index materials in the visible and near infrared (NIR) wavelength range are of interest for a variety of nanophotonic applications such as visible and NIR reflectors, transmitters, vertical-cavity surface-emitting lasers, beam steering, phase changing metasurfaces, and high quality factor resonators [1,2,3,4,5,6,7]
We found for our sputtering system an optimized deposition rate ratio about a 3:4 of Al:Sb at 100 Watts of DC power supplied to the Al target and 50 Watts of RF power supplied to the Sb target
AlSb exhibits a high index of refraction and near zero absorption coefficient in the visible and NIR, making it an interesting material to explore for applications in high contrast nanophotonics
Summary
High refractive index materials in the visible and near infrared (NIR) wavelength range are of interest for a variety of nanophotonic applications such as visible and NIR reflectors, transmitters, vertical-cavity surface-emitting lasers, beam steering, phase changing metasurfaces, and high quality factor resonators [1,2,3,4,5,6,7]. Ideal materials for these applications need to have both a high index of refraction, in order to create the contrast necessary for the respective photonic phenomena, and a low absorption coefficient.
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