Femtosecond laser damage resistance of oxide and mixture oxide optical coatings

Abstract

We report on the laser damage resistance of ion beam-sputtered oxide materials (Al2O3, Nb2O5, HfO2, SiO2, Ta2O5, ZrO2) and mixtures of Al2O3-SiO2, Nb2O5-SiO2, HfO2-SiO2, Ta2O5-SiO2, and ZrO2-SiO2, irradiated by single 500 fs pulses at 1030 nm. Laser-induced damage threshold (LIDT), refractive index, and bandgaps of the single-layer coatings are measured. For pure oxide materials a linear evolution of the LIDT with bandgap is observed. The results are in accordance with our simulations based on photo-ionization and avalanche-ionization. In the case of mixtures, however, deviations from the previous behaviors are evidenced. The evolution of the LIDT as a function of the refractive index is analyzed, and an empirical description of the relation between refractive index and LIDT is proposed.

Optical breakdown of multilayer thin-films induced by ultrashort pulses at MHz repetition rates

“…5(b); the green dotted lines represent the respective error bars. Although our measurements are in a relatively good quantitative agreement with the so-modified results from [5], they clearly follow a different trend [ Fig. 5(b)].…”

“…However, to the best of our knowledge, currently no study exists on the kHz ultrashort-pulse LIDT at 1030 nm of the materials examined here. Therefore, we weigh our results against the ones reported in [5] for single 500 fs pulses at 1030 nm. To make a fair comparison, we modified the results from [5] in two aspects: (i) to compensate for the difference in pulse duration by using the k τ law, where…”

“…The linear dependence reported in [5] modified in such way is depicted as green dashed line in Fig. 5(b); the green dotted lines represent the respective error bars.…”

“…Therefore, one can expect that the damage threshold of a QWOT stack is constrained by the breakdown threshold of its high-index material. [5], whereas the band gap of TiO 2 was found in [28]. Evidently, even though the breakdown threshold of a quarter-wave stack scales to some extent with the band gap of its high-index material, the dependence is nonlinear.…”

“…This fact has motivated extensive studies of ultrashort-pulseinduced optical breakdown of thin-films over the last decade [1][2][3][4][5][6]. All of them have been carried out by measuring the damage threshold at a low average power, either in single-shot mode or by using a pulse train at a kHz repetition rate.…”