Laser Ablation of Polymethylmethacrylate (PMMA) by Phase- Controlled Femtosecond Two-Color Synthesized Waveforms

Abstract

Single-shot laser ablation of polymethylmethacrylate (PMMA) was studied using dualcolor waveform synthesis of the fundamental (ω) and its second harmonic (2ω) of a femtosecond Ti: Sapphire laser. Changing the relative phase of the fundamental (ω) and second-harmonic (2ω) outputs of the exciting laser resulted in clear modulation of the ablated area. The modulation as well as the dependence of the ablation threshold on the relative phase between the ω and 2ω beams correlated closely with the theoretical model of laser breakdown (ablation) of transparent materials through photoionization in the intermediate regime (Keldysh parameter γ ≈ 1.5). Our study illustrates the potential applications of using phase-controlled synthesized waveform for laser processing of materials.