Assessment of thermally induced shear stress and its effect on pattern waviness in CO2 laser ablation of birefringent polymers

Abstract

This article presents the application of custom-designed poledioscope for dynamic measurement of thermally induced shear stress, as a technique for monitoring waviness of the microscale patterns created using CO2 laser, directly over optically birefringent polymers. Laser ablation experiments were conducted for three optical grade polymers: ethylene vinyl acetate, poly methyl methacrylate, and allyl diglycol carbonate under varying laser power and scanning speeds. A poledioscope, customized by incorporating beam splitter in place of rotating analyzer section of conventional polariscope, was used to assess the thermally induced shear stress on the materials in real time. The waviness of the profile of groove patterns was measured using a profilometer. The shear stress mapping and the profile waviness data recorded for range of laser processing parameters were further analyzed to determine that high thermally induced shear stress results in significant damage on waviness of the lased profile.