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Abstract: The damage probability and damage morphology of the multilayer dielectric films under two wavelengths simultaneous irradiation are investigated. The damage morphology result shows that both pit number and depth caused by simultaneous 1ω and 3ω irradiation increase sharply compared with 3ω irradiation alone. The damage probability results demonstrate that the damage probability magnification ratio of the coupled wavelengths is bigger than 1, especially when 1ω and 3ω all held at near LIDT, the magnification ratio of the damage probability is 7–8, and these results are similar to a recent muti-wavelength damage study about KDP crystal. [Copyright &y& Elsevier]

Abstract: Laser damage behaviors of thin-film beam splitters for third harmonic separation were investigated under the simultaneous exposure of fundamental frequency (1ω) and the third harmonics laser beam (3ω). The samples were prepared by conventional e-beam evaporation, and the surface laser-induced damage thresholds (LIDT) of the samples were obtained for the irradiations of 3ω only and 3ω with various fluence of 1ω. It was found that external 1ω can raise damage probability of multilayer films; the higher the 1ω energy density, the lower the damage threshold. Additionally, numerical simulation of damage probability was given for the simultaneous exposure to two beams. [Copyright &y& Elsevier]

Plate laser beam splitter (PLBS) coatings for intensity-splitting in high-power laser applications face increasing requirements, where the challenge is to simultaneously satisfy a given transmittance (T)/reflectivity (R) intensity-splitting ratio with a certain bandwidth, and a high laser damage threshold (LIDT). Traditionally, a given T/R ratio is achieved by using a non-quarter-wave design. We propose a quarter-wave design strategy for arbitrary T/R ratios by using mixture layers with tunable refractive index (n) and optical bandgap as high- n layers. Two quarter-wave PLBS coatings based on HfO 2 –Al 2 O 3 mixture with a designed T/R ratio of 50:50 are experimentally demonstrated and compared with the traditional PLBS coating. The mixture-based PLBS coating shows good spectral performance, low surface roughness, and high LIDT. For an s -polarized 8 ns pulse laser at a wavelength of 1064 nm, a mixture-based PLBS coating design can improve LIDT by a factor of ∼ 2 with a slightly wider bandwidth. This tunable mixture-based PLBS coating design strategy provides support for the increasingly high output power of high-power laser systems. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a reflecting polarizing beam splitter (RPBS) with a metal-multilayer dielectric grating (MMDG) structure is designed by using a genetic algorithm and the Fourier mode method. The proposed RPBS grating can be operated at a central wavelength of 1053nm. Moreover, this grating can reflect the transverse electric wave in the -1st order and the transverse magnetic wave in the 0th order. The optimized RPBS grating has high extinction ratios of over 20dB from 1030nm to 1076nm at angles ranging from 48.6° to 55.1°. At 1053nm, the highest efficiency of over 98%, as well as polarization extinction ratios of the 0th order and -1st order at 62.2dB and 48.8dB, respectively, is obtained. The optimized MMDG structure shows acceptable tolerances for grating fabrication. This MMDG may be a potential RPBS candidate for use in different optical systems. [Copyright &y& Elsevier]

• Three-dimensional spatially and temporally resolved method for accurate defect damage thresholds of optical films. • Defects on substrate are significant sources of splitter film damages. • Defect damage threshold of 532 nm laser decreases continuously with 1064 nm laser fluence increases. In this paper, we propose a three-dimensional spatially and temporally resolved method for measuring laser-induced damage fluence by identifying the time onset of defect damage and the damage location in the three-dimensional coordinate system of a Gaussian beam. When considering a second-harmonic beam splitter as an example, the defect fluence of fundamental wave (1064 nm) and second harmonic wave (532 nm) simultaneous irradiation is captured accurately by the proposed method. The defect damage threshold of a second-harmonic beam splitter and the coupling effect between multi-wavelength lasers during defect damage initiation are investigated. Our test method can not only identify complex multi-wavelength laser coupling damage mechanisms that traditional test methods cannot observe, but also provides a new method for obtaining accurate defect information for optical films, which is helpful for improving the laser resistance ability of optical films. [ABSTRACT FROM AUTHOR]