Picosecond laser damage thresholds of materials for high-peak-power LWIR laser applications

Ultra-intense laser systems in the long-wavelength infrared (LWIR) spectral region have opened doors to new physics in accelerator research, primarily due to favorable quadratic scaling of the ponderomotive potential with the laser wavelength. Although there is a growing demand for higher peak-power in ultra-fast laser science, its progress is limited by the onset of nonlinear optical effects and laser-induced damage to optical components, which can degrade laser performance. Numerous studies have explored these properties in the ultra-violet to mid-infrared wavelength range using ultra-short-pulsed lasers, but their manifestation at longer wavelengths remains under explored. Consequently, there is a lack of reliable data on materials’ nonlinear properties and laser damage thresholds under ultra-short LWIR pulses near a 9 µm wavelength. This research presents preliminary damage threshold measurements for selected transparent LWIR laser optics and mirrors. Experiments were conducted in air for high-peak power 9.2 µm laser pulses with durations switchable between 2 ps and 70 ps. Samples were characterized ex-situ using optical microscopy to estimate the damage areas, which scale linearly with the logarithm of pulse energy for near-Gaussian beams. Observations reveal distinctive damage thresholds and morphologies caused by the two pulse duration regimes, with no clear scaling with the laser pulse width due to sample-to-sample variations. This laser-induced damage data is crucial for the design of future laser sub-systems such as post-compressors and contributes to the fundamental understanding of material responses to ultra-intense LWIR laser pulses.