Advanced in-situ diagnostics of ultra short pulsed micromachining in glass

摘要

Micro structuring of transparent materials with ultra short pulsed laser radiation is nowadays an established and widely used processing method. However, process optimization, such as the reduction of cracks and defects as well as achieving an increased throughput, remains a challenging task. A general approach requires a detailed knowledge of the underlying mechanism of the laser material interaction. For this purpose, in-situ microscopy offers comprehensive insight into the spatial and temporal characteristics of the nonlinear absorption and subsequent thermalization or relaxation phenomena, respectively. To pursue this approach and analyze various damage mechanisms in a subtractive micromachining process, we apply a novel pump probe microscopy setup, which enables us for the first time to examine an extended parameter range. We present in-situ data of the nonlinear interaction region in glass on a micrometer scale with a temporal resolution of approximately 200 fs comprising the laser material interaction from femtoseconds to microseconds. Our investigations are carried out for incubation and accumulation processing regimes up to a repetition rate of 1 MHz. Additionally, pump pulse durations between 300 fs to 20 ps, as well as several burst operation modes are accessible with our experimental setup. Our extensively automated pump probe setup enables us to reconstruct the material extinction response to analyze the complex absorption profiles. In this context, we report on flexible processing strategies and exemplarily processing results.