Lithium thioindate (LiInS2) is a new nonlinear chalcogenide biaxial material transparent from 0.4 to 12 µm, that has been successfully grown in large sizes and good optical quality. We report on new physical properties that are relevant for laser and nonlinear optics applications. With respect to AgGaS(e)2 ternary chalcopyrite materials, LiInS2 displays a nearly-isotropic thermal expansion behavior, a 5-times larger thermal conductivity associated with high optical damage thresholds, and an extremely low intensity-dependent absorption allowing direct high-power downconversion from the near-IR to the deep mid-IR. Continuous-wave difference-frequency generation (5-11 µm) of Ti:sapphire laser sources is reported for the first time.

International audienceAn experimental and numerical study of the laser-induced damage of the surface of optical materialin the femtosecond regime is presented. The objective of this work is to investigate the differentprocesses involved as a function of the ratio of photon to bandgap energies and compare the resultsto models based on nonlinear ionization processes. Experimentally, the laser-induced damagethreshold of optical materials has been studied in a range of wavelengths from 1030 nm (1.2 eV) to310 nm (4 eV) with pulse durations of 100 fs with the use of an optical parametric amplifier system.Semi-conductors and dielectrics materials, in bulk or thin film forms, in a range of bandgap from 1to 10 eV have been tested in order to investigate the scaling of the femtosecond laser damagethreshold with the bandgap and photon energy. A model based on the Keldysh photo-ionizationtheory and the description of impact ionization by a multiple-rate-equation system is used toexplain the dependence of laser-breakdown with the photon energy. The calculated damage fluencethreshold is found to be consistent with experimental results. From these results, the relativeimportance of the ionization processes can be derived depending on material properties and irradiationconditions. Moreover, the observed damage morphologies can be described within the frameworkof the model by taking into account the dynamics of energy deposition with one dimensionalpropagation simulations in the excited material and thermodynamical considerations

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.

Laser damage phenomena are governed by a number of different effects for the respective operation modes and pulse durations. In the ultra short pulse regime the electronic structure in the dielectric coating and the substrate material set the prerequisite for the achieved laser damage threshold of an optical component. Theoretical considerations have been done to assess the impact of contributing ionization phenomena in order to find a valid description for laser-induced damage in the femtosecond (fs) domain. Subsequently, a special set of sample has been designed to verify these considerations via ISO certified laser damage testing. Examining the theoretical and experimental data reveals the importance of multi-photon absorption for the optical breakdown. For titania, the influence of multi-photon absorption has been clearly shown by a quantized wavelength characteristic of the laser damage threshold.

Spectral dependences of the THz radiation from the laser-illuminated surfaces of InAs and InSb have been investigated experimentally at high optical fluences for the laser wavelengths ranging from 0.6 to 2μm. Efficient THz generation was discovered in the excitation range around 1.6μm. The influence of the intervalley scattering was clearly evidenced. The energy position of the subsidiary conduction band valleys was evaluated from this study to be equal 1.08 and 0.53 eV for InAs and InSb, respectively. It has been concluded that THz emission at high excitation fluencies is dominated by the shift current effect.