High-efficiency, cryogenic-compatible grating couplers on an AlN-on-sapphire platform through bottom-side coupling
Year: 2024
Type: article
Abstract: Sapphire is a commonly used substrate for wide-bandgap III-nitride photonic materials. However, its relatively high refractive index results in low transmission efficiency in grating couplers. Here, we propose and demonstrate that the transmission efficiency can be significantly enhanced by bottom-side coupling. A metal reflector is deposited on the top side of the chip, and the fiber array is glued to the bottom side of the substrate. We experimentally achieve a transmission efficiency as high as 42% per coupler on an aluminum nitride (AlN) on a sapphire platform at the telecom wavelength. In addition, the grating couplers show a robust performance at a cryogenic temperature as low as 3 K for both transverse-electric (TE) and transverse-magnetic (TM) modes. Our results can be useful to a wide range of sapphire-based applications that require low coupling loss and cryogenic operation.
Source: Optics Letters
DOI: 10.1364/ol.549201
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funder: Army Research Office
Award: G3155409136
OpenAlex ID: W4405734472