Dual-wavelength ultra-short pulse laser damage testing

Abstract

In the femtosecond regime laser damage thresholds are often determined by the electric field distribution within the optical component. Commercially available ultra-short pulse laser systems provide ever increasing output powers in fundamental and harmonic wavelengths. Therefore, an increasing demand for frequency conversion or multiwavelengths optics with high damage thresholds for both, fundamental and second harmonic wavelengths is given. These optics are under increased strain and face even more design difficulties. Also, the electric field distribution is of higher complexity and favors multi-photon excitation of high efficiencies. We investigate the LIDT of dichroic high reflecting mirrors under simultaneous exposure to fundamental and second harmonic radiation. As laser source we use a Ti:Sa system delivering sub 200 fs pulses at 780nm/390nm. A delay-line was incorporated to ensure temporal overlap of the 2 pulses in the test plane. Further, the LIDT of a single layer of Ta₂O₅ under irradiation with fundamental and second harmonic radiation is calculated and results are compared with our experiment.