Laser-induced damage of optical thin films submitted to 343, 515, and 1030 nm multiple subpicosecond pulses Dam-Bé Douti Laurent Gallais Mireille Commandré Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 05/15/2015 Terms of Use: http://spiedl.org/termsLaser-induced damage of optical thin films submitted to 343, 515, and 1030 nm multiple subpicosecond pulses Abstract. Optical materials submitted to multiple subpicosecond irradiations are known to exhibit a decrease of the laser-induced damage threshold (LIDT) with the applied number of pulses, an effect referred to as "fatigue" or "incubation." In this work, we experimentally investigate this effect for the case of optical thin films submitted to multiple exposures with 500 fs pulses at different wavelengths: 1030, 515, and 343 nm. Niobia, hafnia, and silica films made with dense coating techniques (magnetron sputtering, ion-assisted deposition, and reactive low voltage ion plating) are studied, as well as the surface of a fused silica substrate. These samples have been exposed to different pulse numbers (from 1 to 100,000) at a low-frequency repetition rate (less than 1 kHz) and the LIDT has been measured. The results reveal the differences between materials and for the various wavelengths such as the decrease rate of the LIDT or the stabilization level that is reached after multiple exposures. All the results evidence the role of native-and laser-induced defects that we discuss on the basis of published works on the subject. Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 05/15/2015 Terms of Use: http://spiedl.org/terms

We investigate phase imaging as a measurement method for laser damage detection and analysis of laser-induced modification of optical materials. Experiments have been conducted with a wavefront sensor based on lateral shearing interferometry associated with a high-magnification optical microscope. The system has been used for the in-line observation of optical thin films and bulk samples, laser irradiated in two different conditions: 500 fs pulses at 343 and 1030 nm, and millisecond to second irradiation with a CO2 laser at 10.6 μm. We investigate the measurement of the laser-induced damage threshold of optical material by detection and phase changes and show that the technique realizes high sensitivity with different optical path measurements lower than 1 nm. Additionally, the quantitative information on the refractive index or surface modification of the samples under test that is provided by the system has been compared to classical metrology instruments used for laser damage or laser ablation characterization (an atomic force microscope, a differential interference contrast microscope, and an optical surface profiler). An accurate in-line measurement of the morphology of laser-ablated sites, from few nanometers to hundred microns in depth, is shown.

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We report on the realization of aluminum oxyfluoride thin films and alumina/silica mixture coatings with different ratios by ion beam sputtering. The atomic compositions quantified by energy dispersive x-ray spectroscopy are correlated with the optical properties calculated from spectrophotometry and laser calorimetry measurements. Furthermore, the femtosecond laser damage resistance (τ=400  fs) of single layers is investigated in the infrared at 1030 nm and in the ultraviolet at 343 nm wavelengths. Experimental results on the wavelength scaling of the laser-induced damage threshold for oxyfluoride and oxide composite coatings are presented.