The damage initiation and damage-growth behavior of dielectric mirrors suitable for operation in the ultraviolet (351-nm) spectral range is investigated as a function of the dielectric materials involved, optics design, beam polarization, and pulse duration. The aim of this effort is to understand the optimal designing parameters of transport mirrors for nanosecond pulses in the near-ultraviolet spectral range. The results provide insight into processes that affect the damage-growth resistance resulting from material modifications during damage initiation.
Laser-induced contamination (LIC) degrades the performance of optical components and can result in optical losses or even laser-induced damage. LIC deposit formation limits reliable operation of high repetition rate industrial lasers. In this work, we investigate LIC growth on dielectric oxide thin films in air environment irradiated by MHz sub-ps laser at 515 nm. We study the LIC growth dynamic in dependence on thin film deposition method, thin film material and thin film thickness.
Crystalline sesquioxide films (Sc2O3, Y2O3, Lu2O3) produced by pulsed-laser deposition were examined for laser damage resistance with pulses of 500 fs duration, at a wavelength of 1030 nm and at a 10 Hz repetition rate. Comparable tests were performed with amorphous magnetron-sputtered thin films (SiO2, HfO2, Nb2O5). We found the laser-induced damage thresholds of the sesquioxides are close to those of HfO2 in the multi-pulse test regime. The results are the basis for designs of damage resistant re ective components used in ultrashort-pulse lasers.
Dielectric sesquioxide films (Sc2O3, Y2O3, and Lu2O3) were fabricated by pulsed-laser deposition and tested in terms of their laser damage properties for pulses of 500 fs duration, at a wavelength of 1030 nm and at a 10 Hz repetition rate. Comparable tests were performed with magnetron-sputtered thin films of established optical-coating materials (SiO2, HfO2, and Nb2O5), whose results served as a benchmark. The laser-induced damage thresholds of the sesquioxides are comparable to each other, and in the multi-pulse test regime show values close to ones of HfO2 coatings. A lower damage threshold was observed for the polycrystalline Lu2O3 film grown on sapphire compared to single-crystal Lu2O3 grown on yttrium aluminium garnet (Y3Al5O12), attributed to the highly textured morphology and potential for a greater density of defect states in these films. We conclude that pulsed-laser deposition is a potential fabrication method of sesquioxides for use in high-power resistant optical components for ultrashort-pulse lasers.
Laser-induced contamination (LIC) can lead to optical losses or laser-induced damage on optical components and limits the reliable operation of high repetition rate industrial lasers. In our work, we used MHz sub-ps laser source at 515 nm to test dielectric oxide materials in air environment in terms of LIC formation. We found significant difference in the LIC deposit rate in dependence on coating material and deposition technique. The results could be used for new designs of optical components that will be more resistant to LIC formation.
Laser-induced damage experiments on HfO2 and Nb2O5 were performed with 500 fs pulse duration at 1030 nm wavelength. Threshold fluences in dependence of beam size have been determined within the range of effective beam diameters from 40 µm up to 220 µm. The results suggest no dependence of beam size effect on effective beam diameters at least between 80 µm to 160 µm. The LIDT results indicate importance of appropriate focusing conditions and beam measurement to qualify the optics for use in lasers with large beam sizes.
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