Thermal stress analysis of the microtoroid under CO2 laser

The planar microtoroid with unique whispering gallery mode (WGM) has ultra-high Q value (UHQ) and better optical property. In order to get the UHQ cavity, it is very important to deal with the surface of microtoroid using CO₂ laser reflow during the fabrication process. Because of the TEM₀₀ laser output, there will be thermal stress which affects the Q value badly. In this paper, we design physical model and analyze the temperature distribution theoretically. Furthermore, thermal stress of different microtoroids has been tested with Raman Spectral Analyzer. At last we found that when the optical path is stabile and the lens is fixed the output power in the 7/1000 duty cycle of 30 minutes long pulse will have a good result.