The linear electro-optic coefficient of lithium niobate on insulator (LNOI) thin films has been characterized over a broad range of modulation frequencies from 50 MHz to 270 GHz. A coefficient of 25-30 pm/V was found.

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 incorporate Fourier surfaces into silicon waveguides with vertical tapers for next-generation photonic grating couplers. By combining thermal scanning-probe lithography and reactive-ion etching, we generate gratings with smoothly apodized depth profiles and multi-wavelength coupling functionality.

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.

The Pockels coefficients in thin-film barium titanate (BTO) and lithium niobate (LN) have been measured for modulating frequencies up to 300 GHz. BTO’s effective nonlinearity is ~10 times larger than LN’s with a small frequency dependence.