Wavelength dependence of femtosecond laser-induced damage threshold of optical materials

Abstract

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

Wavelength dependence of femtosecond laser-induced breakdown in water and implications for laser surgery

“…Now an avalanche-like behavior was found for irradiance conditions above the ablation threshold both with the multiple-rate-equation model and the kinetic approach [38]. In several recent studies on optical breakdown in large-band-gap solids, effective collision times ≤ 1 fs were used, and the results consistently revealed a large influence of AI, in agreement with our results on water [27,29,31,39,47].…”

“…The wavelength dependence of fs breakdown in band-gap solids has been investigated in several studies [29,34,[46][47][48] but no detailed study on the wavelength dependence of fs breakdown in water is yet available. Olivié et al measured I th at the surface of corneal tissue at eight wavelengths between 800 nm and 1400 nm and interpreted the I th (λ) trend using a breakdown model for water [49].…”

Selective laser melting of hypereutectic Al-Si40-powder using ultra-short laser pulses

“…To determine the damage/ablation threshold of materials in ultra-short laser pulse processing, the energy density or the so-called fluence is used. The single pulse ablation threshold fluence of aluminium and silicon at 1030 nm is approximately 0.12 J cm 2 in the sub-picosecond regime [31,32]. For shorter laser wavelengths, the silicon particles linearly absorb the laser radiation which strongly decreases the threshold for ablation [31].…”

Automatic classification of true and false laser-induced damage in large aperture optics

“…[1][2][3] When the number of damaged sites increases to a certain magnitude, these sites modulate the high-power UV lasers in ICF experiments, thereby significantly affecting the beam quality. [4][5][6][7] The best way to rapidly and efficiently detect and track the damage on an FOA surface is to design an online imaging system for observing tiny defects in the center of the target chamber. From the literature published in recent years, there are mainly two research teams in the field of damage online detection in ICF experiments for large aperture optics: the Lawrence Livermore National Laboratory (LLNL) and the China Academy of Engineering Physics (CAEP).…”