Micromachining of transparent materials with super-heated liquid generated by multiphotonic absorption of organic molecule

Micromachining of transparent materials with a well-defined pattern of lines and spaces was carried out by laser-induced backside wet etching (LIBWE). The etch rate of a fused silica plate ranged from 5 to 25 nm/pulse with a KrF laser irradiation from 400 to 1300 mJ/cm2, using an acetone solution containing pyrene at a concentration of 0.4 mol/dm3. Threshold fluences for etching of fused silica and calcium fluoride plates were 240 and 740 mJ/cm2, respectively, which are remarkably lower than those with conventional KrF laser ablation. The mechanism for etching is explained by the attack of super-heated molecules generated by laser ablation of a pyrene–acetone solution during cyclic multiphotonic absorption.