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New nonlinear laser effects in α-quartz: generation of a two-octave Stokes and anti-Stokes comb and cascaded lasing in the spectral range of the second and third harmonicsa Federal Scientific Research Center "Crystallography and Photonics", Russian Academy of Sciences, Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninskii prosp. 59, Moscow, 119333, Russian Federaion b Institut für Kristallographie, Universität zu Köln, Zulpicherstr. 49b, Köln, D-50674, Germany c Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstr. 36, Berlin, D-10623, Germany Crystals that are simultaneously χ(2)- and χ(3)-active offer a wide range of possibilities for the generation of new coherent wavelengths of light. Frequency conversion processes such as stimulated Raman scattering, second and third harmonic generation, or parametric sum and difference frequency mixing can be combined effectively in the same noncentrosymmetric crystal in cascaded χ(3) ↔ χ(2) lasing processes. We present several new manifestations of these effects under picosecond laser excitation in α-quartz (SiO2), the oldest nonlinear-laser crystal. Among them are 45 Stokes and anti-Stokes wavelength comb generation of more than two octaves (from 0.3692 μm to 1.5142 μm) and self-conversion of Raman-generation frequencies into the wavelength region of the second and third harmonics of one-micron pumping via many-step cascaded χ(3) ↔ χ(2) processes.
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