Wideband Dispersion Flattening for Whispering Gallery Mode Microresonators Fabricated by Laser Micromachining

Dispersion engineering of microresonators is very important for applications, such as optical comb generation which desires wideband flat and small dispersion. In this paper, dispersion investigation has been carried out for whispering gallery mode (WGM) microresonators fabricated by laser micromachining. The dispersion properties of WGM microresonators fabricated by CO
₂
and femtosecond lasers have been comprehensively studied by finite element method for different geometries. Significantly flattened dispersion curves have been obtained for both microresonators fabricated by CO
₂
laser and femtosecond laser with optimized geometries. The belt-like resonator fabricated by femtosecond laser has better flattened small dispersion which is only between 0 and 4 ps/(nm · km) within the wavelength range from 1300 to 1800 nm, comparable to that of a zero dispersion flattened fiber. The results are of great significance for guiding the WGM microresonator fabrication for optical comb generation applications.