We introduce efficient polarization-insensitive SiN O-band grating coupler relying on a simple fabrication procedure. It's an essential but missing building block in photonics and needed, for example, to realize detectors for light with unknown polarization.

We demonstrate low-loss fiber-to-chip coupling via a-Si grating couplers on top of SiN waveguides for C-band TE light. The suggested simple scheme is fabrication tolerant and offers a path towards coupling efficiencies above -1 dB.

We report a simple implementation of integrated polarization rotator for thick-film SiN platform for S-/C-/L- bands operation. The fabricated devices show high polarization conversion efficiency above 90% and broadband operation.