Quality improvement and mode evolution of high-Q lithium niobate micro-disk induced by “light annealing”

High-quality factor microresonators are a key component in photonic integrated circuits. However, it is more difficult to precisely engineer a single component after fabrication as integration density gets higher. In this work, we improve the quality factor of the fabricated resonator by femtosecond laser shots. The high repetition laser pulses scatter into the cavity, and then the localized high-density light field introduces a light refining and “annealing” process that may restore the lattice disorders. The intrinsic quality factor of a measured mode can be promoted from 2.17×10 5 to 1.84×10 6. Moreover, increasing the shot power may kill the high order modes, and only the fundamental mode survives. This method may inspire new potential application in femtosecond laser modification in photonic integrated circuits.