Polarization rotator and switch on thin-film lithium niobate

Polarization rotators (PRs) and polarization switches are essential for on-chip polarization control. However, high-performance implementations remain scarce on the thin-film lithium niobate (TFLN) platform, despite its recent emergence as a promising photonic platform. Here, we propose and experimentally demonstrate a PR based on two supermode converters and a compact asymmetric phase shifter. By electro-optically tuning the phase shifter, a polarization switch is further realized. At 1550 nm, the PR exhibits low insertion losses (ILs) of 0.37 dB and 0.41 dB with polarization extinction ratios (PERs) of 31.78 dB and 20.4 dB for TE 0 and TM 0 inputs, respectively. It maintains PER >20 dB and IL <1 dB under ±10 nm width variation in one arm of the phase shifter across the 1510–1610 nm range, demonstrating large fabrication tolerance. The polarization switch achieves a PER >20 dB and an IL <2.2 dB across a 140 nm bandwidth (1490–1630 nm), with a sub-13 ns response time and ultra-low power consumption (∼0.008 mW ). These results enable scalable and efficient polarization control on the TFLN platform.