The lifetime of optical components submitted to high laser fluences is decreased under organic contaminated
environment. Our previous studies have shown that chemical species outgassed from materials present in the laser
environment of the Ligne d’Intégration Laser (LIL) and in the optics packaging (phthalates, silicones, and aromatic
compounds) are potential contaminants for optics. In order to avoid the presence of such molecules in the Megajoule
Laser (LMJ) environment, a new comprehensive program is started up using a qualified Micro-chamber/Thermal
Extractor (M-CTE250 Markes International) for controlled contaminations of optics. The final target is the development
of a qualification procedure to determine the compatibility of materials used for the building of the LMJ with the LMJ
optics. First results of this program will be presented.
We report on the laser damage resistance of thin films prepared by Ion Beam Sputtering. The samples are fused silica
substrates coated with single layer films of pure oxides (SiO2, Nb2O5, ZrO2, HfO2, Ta2O5, Al2O3, Sc2O3) and oxide mixtures with various ratios (Nb2O5/SiO2, ZrO2/SiO2, HfO2/SiO2, Ta2O5/SiO2, Al2O3/SiO2 and Sc2O3/SiO2). For this study the LIDT of more than 60 different samples have measured at 1030nm with pulse durations of 500fs with single pulse irradiation. The results are expressed and compared in terms of LIDT as a function of the measured band gap
energy and refractive index. For simple oxide materials a linear evolution of the LIDT with bandgap is observed, with the exception of Sc2O3 material where a very high damage threshold is observed, compared to other high index materials. In the case of mixtures, a more complex behavior is evidenced.
The femto-second technology gains of increasing importance in industrial applications. In this
context, a new generation of compact and low cost laser sources has to be provided on a commercial
basis. Typical pulse durations of these sources are specified in the range from a few hundred femtoup
to some pico-seconds, and typical wavelengths are centered around 1030-1080nm. As a
consequence, also the demands imposed on high power optical components for these laser sources
are rapidly increasing, especially in respect to their power handling capability in the ultra-short pulse
range. The present contribution is dedicated to some aspects for improving this quality parameter of
optical coatings. The study is based on a set of hafnia and silica mixtures with different compositions
and optical band gaps. This material combination displays under ultra-short pulse laser irradiation
effects, which are typically for thermal processes. For instance, melting had been observed in the
morphology of damaged sides. In this context, models for a prediction of the laser damage
thresholds and scaling laws are scrutinized, and have been modified calculating the energy of the
electron ensemble. Furthermore, a simple first order approach for the calculation of the temperature
was included.
We report an experimental investigation in the laser-induced damage threshold (LIDT) of optical coatings materials. The
samples are single layers of Al2O3, Nb2O5, HfO2, SiO2, Ta2O5, ZrO2 deposited through different deposition techniques
(evaporation or sputtering with/without ion assistance) and mixtures of Al2O3/SiO2, Nb2O5/SiO2, HfO2/SiO2, Ta2O5/SiO2 and ZrO2/SiO2 on silica substrates. The LIDT is measured at 1030nm, 500fs in single shot mode. The results are
expressed and compared in term of LIDT as a function of bandgap and LIDT as a function of refractive index.
Single shot LIDT of single layer coatings of different deposited materials (SiO2, HfO2, Ta2O5 and Nb2O5) have been
studied. We report dependence of the damage threshold with different operational and material parameters (pulse
duration, nature of the deposited material, deposition process or thickness of the layer). For interpretation a model
dedicated to optical coatings and based on the conduction band electron rate equation is used. The simulations are
compared to experiments. The theoretical approach is in good accordance to the experimental data.
In this study, we report on our recent progress in research of single layer mixed zirconia-silica and niobia-silica
composite coatings prepared by Ion Beam Sputtering technique. All coatings of the same optical thickness
were characterized in terms of reflection/transmission spectrometry, X-ray diffraction, atomic force and optical
microscopy, optical back-scattering and optical resistance (laser-induced damage threshold - LIDT) in subpicosecond
mode. The optical resistance, TIS and LIDT results reveal clear dependence on high refractive index
material content in composite coating and its crystalline structure. The results are interpreted and discussed
by the means of different models available in literature.
A new instrument dedicated to laser damage measurement in subpicosecond scale has been developed at the Fresnel
Institute (3 ps to 100 fs, 1030 nm). The objective of this work is to realize a comparative study of the behavior of hafnia
thin films prepared by different techniques (Reactive Low Voltage Ion Plating, Electron Beam Deposition, Dual Ion
Beam Sputtering) under subpicosecond pulse irradiation in the near infra red. Laser-induced damage thresholds are
measured for one-on-one procedures. Laser damage setup and first results at 1 ps are presented and initiation
mechanisms are studied thanks to damage morphologies and optical properties characterization. Results show a
dependence of damage threshold with deposition techniques and so with microstructure of the film.
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