Polarization-insensitive 1D unidirectional compact grating coupler for the C-band using a 500 nm SOI

Abstract

Grating couplers are an important optical interconnect and have increasingly found their utility in sensing and LIDARs as well. Optical systems in general have been struggling to increase their bandwidths, making polarization insensitivity highly desirable. The standard 220 nm silicon-on-insulator (SOI) platform used for integrated photonics suffers from physical bottlenecks in the form of large modal differences in effective refractive index, propagation loss, and dispersion. In this paper, we present a grating coupler for polarization-insensitive coupling with polarization-dependent loss of less than 0.2 dB for more than 80% of the C-band on an alternative 500 nm SOI platform. We further show that the same design can be extended to polarization inflexible coupling and can reduce the polarization-dependent loss to less than 0.08 dB for the complete C-band. This platform is devoid of shortcomings, making it better suited for polarization-insensitive photonics, and the coupler is able to achieve these results through a simple and compact 1D design.