Direct comparison of kilohertz- and megahertz-repetition-rate femtosecond damage threshold

Abstract

We performed femtosecond laser-induced damage threshold (fs LIDT) measurements with substantially different repetition rate Ti:sapphire laser systems: a 1 kHz regenerative amplifier and a 4.3 MHz long-cavity oscillator. All other pulse parameters are kept the same. Comparative measurements of a dielectric high reflector, a chirped mirror, and metallic mirrors show at least a factor of 2.7 lower fs LIDT at megahertz repetition rates. We attribute this to thermally assisted damage mechanisms supported by complex heat transfer simulations.

Laser damage of free-standing nanometer membranes

“…It has indeed been seen before that multi-shot illumination can reduce the laser damage threshold by incubation effects, 32 for example, by the formation of laser-induced defects and nano-crackings 33 or by thermal accumulation. 34 The incubation effect usually saturates at a large number of laser shots, typically 10 4 , 33 which is more than two orders-of-magnitude lower than in our experiment. It is therefore likely that the slightly lower damage threshold at 50 kHz is related to a slightly elevated temperature in the laser spot via the associated mechanical stress, although the main mechanism remains to be a singlepulse effect or high-field damage by the laser's electric field.…”

Analysis of laser-induced contamination at 515 nm in the sub-ps/MHz regime

“…5,6 With some optimized designs taking into account these intrinsic properties of the materials it is possible, by avoiding intensity peaks in materials with low Lased-Induced Damage Threshold (LIDT), to enhance significantly the laser damage resistance of multilayer stacks. [7][8][9] However, in the case of high repetition rate lasers other complex processes can lead to the reduction of the laser damage resistance with the number of pulses: generation of electronic defects in the materials that eases the ionization process, 10,11 heat accumulation leading to stress-build-up and potential failure, 12,13 damage growth initiated by localized defects. [14][15][16][17] At this point only laser damage tests in conditions as close as possible to the applications can be used to predict the lifetime of the components and their power handling capabilities.…”

Wavelength-Selective Nonlinear Imaging and Photo-Induced Cell Damage by Dielectric Harmonic Nanoparticles

“…Within this resonant approach, the temperature reached by a ZnO nanowire excited by two photons above the band gap frequency was recently estimated to 327 °C . The amount of temperature increase does not exclusively rely on the choice of the excitation frequency, but also on other parameters playing a role in local heating dynamics, in particular, the numerical aperture (NA) of the focused beam, the laser repetition rate, and the dwell time. , Keeping all other conditions identical, MHz sources are more effective for heating than kHz ones because the interpulse delay is short compared to the heat dissipation rate.…”