Surface ablation of poly allyl diglycol carbonate polymer using high-repetition-rate femtosecond laser

Abstract

Laser ablation (LA) has been acknowledged as a universal laser processing tool to develop new devices. Typically, LA involves removal of material with a high energy femtosecond (fs) laser, which has a relatively low-pulse repetition rate (kHz). This constricts the processing speed to avoid separation between successive pulses during the device patterning. Hence, it is reasonable to use a high-repetition-rate laser as an alternative approach to enable high-speed laser processing. We experimented on the surface ablation of poly allyl diglycol carbonate (PADC) using a high-repetition-rate (MHz) fs laser. The objective of this study is to investigate the laser-ablated pattern on PADC and the effect of the number of laser pulses on the ablation rate. For the purpose of this experiment, straight trenches were formed directly on the PADC surface with 800-nm fs-pulsed laser writing. It was found that the ablation mechanism in the high-repetition-rate regime was primarily controlled by the number of irradiated pulses. At a fixed pulse energy, the ablation rate dropped from 9.6 to 3.4 pm / pulse for 1 × 105 and 8 × 105 pulses, respectively. This outcome stemmed from the disruption of laser focusing via thermally induced surface morphology changes due to excessive energy accumulation.