Mode surgery of LN micro-resonator by femtosecond laser irradiation

TL;DR

This paper demonstrates a femtosecond laser technique to enhance the quality factor of lithium niobate microresonators by repairing surface defects, significantly improving their performance for integrated photonic circuits.

Contribution

It introduces a novel femtosecond laser irradiation method for mode-specific quality factor enhancement in LN microresonators, enabling precise surface defect repair.

Findings

Quality factor improved from 2.17×10^5 to 1.84×10^6

Laser irradiation selectively repairs surface defects

Method offers controllable enhancement for integrated photonics

Abstract

Lithium niobate(LN) microresonator is a key component in photonic integrated circuits. An intriguing phenomenon was observed that the quality factor for specific modes of the resonator can be further improved by femtosecond laser irradiation. The high repetition laser pulses scatters into the cavity by forming a defect on the surface and is confined in the edge. A localized coupled laser refining process will then repair the lattice disorders and tiny burrs on the periphery. The intrinsic quality factor of a measured mode can be promoted from 2.17$\times$10$^5$ to 1.84$\times$10$^6$ indicating one order of magnitude improvement. This highly controllable method has its own unique advantages in improving the quality of an integrated resonator which opens new prospects for single component engineering of LN photonic integrated circuits.