Holographic interferometry for the structural diagnostics of UV laser ablation of polymer substrates

Holographic interferometry is examined for its potential as a diagnostic to ol of the structural modifications effected in laser-processing application s. The interferometric 'comparison' of the holographic images of the sample recorded before and after irradiation enables the full-field spatially res olved detection of the induced structural modifications. The potential of t he method is illustrated in the ablation of polymer (polymethylmethacrylate and polystyrene) films with nanosecond pulses at 193 and 248 nm. The detai led characterization and quantitative monitoring of the growth of the induc ed modifications as a function of laser-material parameters is attained. A most novel result is the observation of delocalised structural modification s at distances relatively far away (d approximate to 2 cm) from the irradia ted area.