Interfacial damage in a Ta2O5/SiO2 double cavity filter irradiated by 1064 nm nanosecond laser pulses

The Laser-Induced Damage Threshold (LIDT) and damage morphologies of a Ta(2)O(5)/SiO(2) double cavity filter irradiated by 1064-nm, 10-ns pulses were investigated. The depths of flat bottom pits were examined by an optical profiler and then calibrated according to the Electric-Field Intensity (EFI) distributions and the cross-sectional micrographs obtained using the Focus Ion Beam (FIB) technology. The statistics for depths of 60 damage sites suggested that the Ta(2)O(5) over SiO(2) interface was more vulnerable to Laser-Induced Damage (LID) than the SiO(2) over Ta(2)O(5) interface. After examining the morphologies of interfacial delaminations carefully, we found that the Ta(2)O(5) over SiO(2) interface instead had stronger mechanical strength. So, the higher density of susceptible defects at the Ta(2)O(5) over SiO(2) interface was considered to be the reason that LID was preferentially initiated at this type of interface. Based on the above findings, a phenomenological model was proposed to describe the formation of flat bottom pits.