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Abstract
The study used linearly and circularly polarized femtosecond pulsed lasers to irradiate a Ta2O5/SiO2 film. Firstly, the damage thresholds of the film for linearly and circularly polarized femtosecond pulsed lasers were measured in 1-on-1 mode. The results showed that the damage threshold (1.70 J/cm2) under a circularly polarized laser was higher than that (1.68 J/cm2) under a linearly polarized laser. For femtosecond lasers, the multi-photon ionization cross-section under circular polarization was lower than that under linear polarization. The lower ionization rate under circular polarization led to a higher damage threshold compared to the case under linear polarization. Secondly, the damage morphology of the film irradiated by linearly and circularly polarized femtosecond lasers was observed by microscope. The damage caused by linearly polarized laser was more evident than that caused by the circularly polarized laser. Finally, the damage thresholds induced by linearly and circularly polarized femtosecond pulsed lasers were measured in S-on-1 (S = 2, 5, and 10) mode. For the same S value (2, 5, or 10), the damage threshold under the circularly polarized laser was higher than that under the linearly polarized laser. The damage thresholds under two polarized laser pulses decreased with an increase in the number of laser shots, indicating that repeated laser pulses had a cumulative effect on the damage of the film.
Highlights
Publisher’s Note: MDPI stays neutralOptical thin film is a critical component in the laser system, and its optical performance determines the quality of laser output to a large extent
The damage threshold threshold of of the the film under linear and circular polarization was obtained, and the damage morphology of film under linear and circular polarization was obtained, and the damage morphology the film under linear and circular polarization was observed by microscope
It was found of the film under linear and circular polarization was observed by microscope
Summary
Optical thin film is a critical component in the laser system, and its optical performance determines the quality of laser output to a large extent. Chen et al studied the melting and thermal-stress damage thresholds of silicon induced by long pulsed laser at 0.532, 1.064, and 10.6 μm [7] and analyzed the damage mechanism of silicon According to their results, the LIDT of silicon with 0.532 μm was lower than that with. 1.064 and 10.6 μm, and the damage mechanism of silicon was mainly the melting damage It can be seen from the above discussion that LIDT is limited by laser parameters, including laser wavelength, pulse width, energy density, spot area, polarization state, etc. It is limited by the characteristics of the film, including the film material, thickness, processing technology, preparation method, etc. The damage threshold of the film for both polarized lasers was obtained, and a microscope observed the damage morphology of the film for both polarized lasers
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