Optical damage threshold in thin-film lithium niobate for high power applications

High-power photonic systems require optical materials that can withstand high optical intensities while maintaining thermal stability and avoiding catastrophic damage. The power levels demanded for directed energy (DE) applications often exceed the tens of kilowatts, which is beyond the current capabilities of photonic integrated circuits (PICs). Fiber lasers have demonstrated multi-kilowatt output powers but lack active control functionalities such as modulation and steering of optical beams. To bridge this gap, hybridization of optical fibers and thin-film lithium niobate (TFLN) is a promising solution. TFLN offers an excellent platform that retains the beneficial properties of bulk lithium niobate, such as a wide transparency window and high nonlinear and electro-optic coefficients, while providing added advantages of tight mode confinement for dense PICs. While managing extreme DE powers on-chip remains elusive, TFLN offers a scalable pathway for interfacing high-power fiber sources with active photonic components. In this work, we characterize and analyze the continuous-wave (CW) material damage threshold of TFLN waveguides to determine the upper limits of their power-handling capabilities. Using lensed fibers for coupling, the damage threshold at the standard telecommunication wavelength of 1550 nm was determined to be approximately 92 MW/cm², which, for standard lithographically defined single-mode waveguides, corresponds to 200–500 mW of guided optical power. These results lay the foundation for future integrated photonic systems capable of high-fidelity modulation, frequency conversion, and control of high-energy optical beams.