Toward compact high-efficiency grating couplers for visible wavelength photonics

Although grating couplers have become the de-facto standard for optical access to integrated silicon photonics platforms, their performance at visible wavelengths, in moderate index contrast platforms such as silicon nitride, leaves significant room for improvement. In particular, the index contrast governs the diffraction efficiency per grating tooth and the resulting overall coupler length. In this work, we develop two approaches to address this problem: a dielectric grating that sums multiple optical modes to increase the overall output intensity; and an embedded metal grating that enhances the attainable refractive index contrast, and therefore reduces the on-chip footprint. We present experimental results that can be developed to realize compact efficient visible wavelength photonic interconnects, with a view toward cryogenic deployment for quantum photonics, where space is constrained and efficiency is critical. (C) 2022 Optica Publishing Group

Automated summary

This paper addresses the performance issues of grating couplers on moderate index contrast platforms at visible wavelengths. Two approaches, a dielectric grating and an embedded metal grating, are proposed to improve the overall output intensity and reduce the on-chip footprint. Experimental results demonstrate the potential of these methods for compact and efficient visible wavelength photonic interconnects, particularly in cryogenic deployment for quantum photonics.