Compact low-half-wave-voltage thin film lithium niobate electro-optic phase modulator fabricated by photolithography-assisted chemo-mechanical etching (PLACE).

We present a compact dual-arm thin-film lithium niobate (TFLN) electro-optic phase modulator fabricated using the photolithography-assisted chemo-mechanical etching (PLACE) technique. The design of the device doubles the modulation amount compared to single-arm modulators while maintaining the same chip length. Achieving a half-wave voltage of approximately 3 V, the device outperforms conventional single-arm phase modulators. Furthermore, the phase modulator exhibits low sensitivity to optical wavelengths in the range of 1510-1600 nm and offers a low insertion loss of 2.8 dB. The capability to generate multiple sideband signals for optical frequency comb applications is also demonstrated, producing 29 sideband signals at an input microwave power of 2 W.