Photothermal microscopy characterization of multiphoton annealing of defects in thin-film coatings for high-power lasers

Facundo Zaldívar Escola; Nélida Míngolo; Oscar E. Martínez; Jorge J. Rocca; Carmen S. Menoni

doi:10.1117/12.2508904

4 March 2019 Photothermal microscopy characterization of multiphoton annealing of defects in thin-film coatings for high-power lasers

Facundo Zaldívar Escola, Nélida Míngolo, Oscar E. Martínez, Jorge J. Rocca, Carmen S. Menoni

Author Affiliations +

Proceedings Volume 10925, Photonic Instrumentation Engineering VI; 1092509 (2019) https://doi.org/10.1117/12.2508904
Event: SPIE OPTO, 2019, San Francisco, California, United States

Abstract

A focus error method photothermal microscope was designed for the simultaneous annealing and characterization of defects in thin film multilayer coatings for high power lasers. The technique relies in the detection of the thermal lens induced by the local absorption of a light power focused laser. A 10W CW laser at 1.06μm wavelength was used as a pump and a HeNe laser at 632.8nm as a probe. A 4 quadrant detector and specifically designed astigmatic optic is used to determine the defocusing of the transmitted probe beam at the modulation frequency of the pump. The instrument scans the surface and detects the evolution of the absorptance with time with sensitivity below 0.1ppm. The pump beam focus determines the spatial resolution of the instrument and the probe beam size, much larger than the pump, has to match the modulation frequency that yields a thermal diffusion distance of the order of the probe beam in one modulation period. The detailed design of the instrument will be presented showing the design parameters that should be considered for an adequate sensitivity. The sensitivity of the system is better than 0.1ppm and allows the realization of spatial sweeps and even measurements of the evolution of absorption as a function of time. These capabilities allow the location of defects and their characterization.

Conference Presentation

Citation Download Citation

Facundo Zaldívar Escola, Nélida Míngolo, Oscar E. Martínez, Jorge J. Rocca, and Carmen S. Menoni "Photothermal microscopy characterization of multiphoton annealing of defects in thin-film coatings for high-power lasers", Proc. SPIE 10925, Photonic Instrumentation Engineering VI, 1092509 (4 March 2019); https://doi.org/10.1117/12.2508904

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