Relaxation of the electro-optic response in thin-film lithium niobate modulators

Thin-film lithium niobate (TFLN) is a promising electro-optic (EO) photonics platform with high modulation bandwidth, low drive voltage, and low optical loss. However, EO modulation in TFLN is known to relax on long timescales. Instead, thermo-optic heaters are often used for stable biasing, but heaters incur challenges with cross -talk, high power, and low bandwidth. Here, we characterize the low -frequency (1 mHz to 1 MHz) EO response of TFLN modulators, investigate the root cause of EO relaxation and demonstrate methods to improve bias stability. We show that relaxation -related effects can enhance EO modulation across a frequency band spanning 1kHz to 20kHz in our devices - a counter -intuitive result that can confound measurement of half -wave voltage (V pi) in TFLN modulators. We also show that EO relaxation can be slowed by more than 104 -fold through control of the LN-metal interface and annealing, offering progress toward lifetime -stable EO biasing. Such robust EO biasing would enable applications for TFLN devices where cross -talk, power, and bias bandwidth are critical, such as quantum devices, high -density integrated photonics, and communications. (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement