Stimulated Raman Scattering in Yttrium, Gadolinium, and Calcium Orthovanadate Crystals with Single and Combined Frequency Shifts under Synchronous Picosecond Pumping for Sub-Picosecond or Multi-Wavelength Generation around 1.2 µm

Measurement of Multi-Stokes Ultrashort Pulse Shapes of Synchronously Pumped Stimulated Raman Scattering on Combined Vibrational Modes in a BaWO4 Crystal

Multi-Stokes ultrashort pulse shapes and their relative positions of synchronously pumped stimulated Raman scattering (SRS) on combined primary and secondary vibrational modes in a BaWO4 crystal are investigated. An original method of its simultaneous measurement with the help of a streak camera has been developed. The structure of SRS pulses at the pulse shortening effect down to the pulse duration, close to the dephasing time of the secondary Raman mode of the BaWO4 crystal, is registered and analyzed for the detuning of the Raman laser cavity length.

Multiwavelength, picosecond, synchronously pumped, Pb(MoO4)0.2(WO4)0.8 Raman laser oscillating at 12 wavelengths in a range of 1128-1360 nm

In this Letter, a mixed Pb(MoO₄)_0.2(WO₄)_0.8 as a new, to the best of our knowledge, active medium with optimized content for a synchronously pumped multiwavelength Raman laser with a combined frequency shift is presented. The unique structure of this crystal resulted in oscillations at 12 closely spaced output wavelengths in a spectral range from 1128 to 1360 nm. The strongest pulse shortening in comparison with nominally pure scheelite-like crystals has been achieved.

Asymmetric spectral broadening of sub-picosecond laser pulse in BaWO4 crystal: interplay of self-phase modulation, stimulated Raman scattering, and orientational Kerr nonlinearity

Spectral broadening of 0.3 ps 515 nm laser pulse in a highly Raman-active BaWO₄ crystal and fused silica demonstrates significantly different behavior with the incident pulse energy. While the broadening in fused silica is fairly symmetric with respect to the pump laser pulse wavelength, the Stokes wing broadening in the BaWO₄ crystal is 2 times wider than that of anti-Stokes wing, the former demonstrating a step-like increase with the pulse energy. To the best of our knowledge, the obtained data are the first clear evidences of the following facts: (i) stimulated Raman scattering with sufficiently high efficiency of conversion to Stokes components slows down spectral broadening induced by self-phase modulation, and (ii) the mechanism of Kerr nonlinearity, which is responsible for self-phase modulation in BaWO₄, is of orientational nature. The nonlinear refraction coefficient and its decay time following from our experiments with BaWO₄ were estimated as n₂≈6.4.10^-15cm²/W and τ_NL≈0.35ps.