21 February 2011 Some properties of the mixed GaS0.4Se0.6 nonlinear crystal in comparison to GaSe
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Two essential advantages can be expected from adding S to the well known nonlinear crystal GaSe: increase of the bandgap value or the short wave cut-off limit and improved hardness. Recently, we confirmed that the non-centrosymmetric structure of GaSe is preserved up to a GaS content of 40 mol. % while the nonlinear coefficient d22 is reduced by only 24%. The increased band-gap results also in higher surface damage threshold. Our preliminary Sellmeier equations for GaS0.4e0.6 were based on refractive index measurements. These equations are refined in the present work by fitting second-harmonic generation and optical parametric amplification phase-matching angle data in the mid-infrared as well as birefringence data in the visible and near-infrared obtained with thin phase retardation plates. The two-photon absorption effect was studied for GaS0.4e0.6 and GaSe using amplified picosecond pulses at 1064 nm, at a repetition rate of 10 Hz. For intensities in the GW/cm2 range, the two-photon absorption coefficient of GaS0.4e0.6 for the o-polarization is 3.5 times smaller than the corresponding coefficient of GaSe. This means that GaS0.4e0.6 could be safely used in Nd:YAG laser pumped nanosecond optical parametric oscillators or picosecond optical parametric amplifiers, without nonlinear absorption losses. The dynamic indentation measurements with Berkovich type indenter of c-cut GaS0.4e0.6and GaSe plates indicate about 30% higher indentation modulus and microhardness of GaS0.4e0.6 in comparison to GaSe.
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Georgi Marchev, Georgi Marchev, Aleksey Tyazhev, Aleksey Tyazhev, Vladimir Panyutin, Vladimir Panyutin, Valentin Petrov, Valentin Petrov, Frank Noack, Frank Noack, Kentaro Miyata, Kentaro Miyata, Michael Griepentrog, Michael Griepentrog, } "Some properties of the mixed GaS0.4Se0.6 nonlinear crystal in comparison to GaSe", Proc. SPIE 7917, Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications X, 79171G (21 February 2011); doi: 10.1117/12.874452; https://doi.org/10.1117/12.874452

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