Zero-Dispersion Phase-Matched Extracavity Parametric Raman CaCO3 Laser Generating 3rd Stokes Single 80-ps Pulse at 1629 nm under Nanosecond Pumping at 1064 nm

Abstract

In [1] a new effect of pulse shortening down to 300 ps of the parametrically generated second Stokes Raman radiation at 1300 nm via depletion of pumping of intracavity stimulated Raman scattering (SRS) conversion in the passively Q-switched Nd:SrMoO 4 parametric self-Raman laser was demonstrated. The second Stokes pulse was generated in the temporal region of the fundamental laser and first Stokes pulses overlap. It was explained by a mechanism of birefringence-phase-matched orthogonally polarized four-wave mixing that resulted in the second Stokes generation with the strongest nonlinear cavity dumping pulse shortening. It was found that this pulse shortening effect takes place for the second Stokes four-wave-mixing generation (λ S2 −1 = λ s 1 + λs 1 − λ L if pumping at λ L of the first Stokes SRS generation λ s −1 = λ L −1 − ν r (where ν R is the Raman frequency of the active crystal) was intracavity allowing spatially uniform depletion of pumping. As a result, the shortened pulse duration was close to the stage of depletion of pumping Δt ≈ 4.4/g I L c, where g is the Raman gain coefficient of the active crystal, I L is the intensity of intracavity pumping, c is the speed of light.