Stimulated Raman Scattering in Alkali-Earth Tungstate and Molybdate Crystals at Both Stretching and Bending Raman Modes under Synchronous Picosecond Pumping with Multiple Pulse Shortening Down to 1 ps

Abstract

Comparative investigation of characteristics of spontaneous and stimulated Raman scattering (SRS) in different alkali-earth tungstate and molybdate crystals at both high and low frequency anionic group vibrations is presented. It has been found that, among these crystals, the SrMoO4 and SrWO4 crystals are the most perspective for SRS generation on both stretching and bending modes of internal anionic group vibrations with the strongest SRS pulse shortening under synchronous laser pumping because of not only highly intense stretching mode Raman line for efficient primary extra cavity long-shifted SRS conversion but also the widest bending mode Raman line for the strongest SRS pulse shortening down to the inverse width of the widest Raman line (~1 ps) at secondary intracavity short-shifted SRS conversion. The strongest 26-fold pump pulse shortening down to 1.4 ps at the Stokes component with the combined Raman shift in the synchronously pumped extra cavity SrMoO4 and SrWO4 Raman lasers has been demonstrated. It was found that synchronously pumped cascade SRS with combined Raman shift is more efficient in the SrWO4 crystal because the bending mode Raman line is more intense relative to the stretching mode Raman line than that in SrMoO4.

Stimulated Raman Scattering in Pb(MoO4)1−x(WO4)x with x = 0, 0.5, 0.8 and 1.0 with Combined Frequency Shifts on High- and Low-Frequency Raman Modes under Synchronous Picosecond Laser Pumping

“…It is also necessary to pay attention to the observed effect of increasing slope efficiency of oscillation from 25.7% to 44.7% for PbMoO 4 and from 20.0% to 33.8% for PbWO 4 with the change of the pumping orientation from E || c to E ⊥ c that is accompanied by increase in the Raman gain with no change of losses. Earlier, similar effect was observed in many synchronously pumped Raman lasers based on GdVO 4 [28], SrWO 4 [18,29], and PbMoO 4 [19] active crystals via a change of the single-pass Raman gain by a change of the crystal length or pumping orientation. A possible explanation of the effect may be the action of synchronous pumping as it was proposed in work [19].…”

“…Figure 2 shows the experimental setup. It is similar to that used in the previous works [17][18][19] using other Raman-active crystals. The Raman laser with an external ring cavity based on each Raman-active crystal under study was synchronously pumped by repetitively pumped, 36-ps, 150-MHz, 330-nJ Nd:GdVO4 laser at a wavelength of λ0 = 1063 nm operating in quasi-continuous regime with the 500µ s. The pumping was single-pass due to high transmission of both concave mirrors (PM and CM) of the Raman laser cavity.…”

“…As in our previous works [17][18][19], SRS oscillation was achieved after precise synchronization of the Raman laser cavity length with the repetition rate of the pump laser. The synchronization must be tuned for each pumping orientation (E || c and E ⊥ c) because of high birefringence of the investigated crystals [19].…”

“…The ν 2 line is significantly wider than the ν 1 line [16]. This allowed to achieve radiation pulse shortening down to the inverse width of the widest ν 2 line in transient SRS with combined (ν 1 + ν 2 ) frequency shifts in the scheelite-type crystal series under synchronous pumping by repetitive picosecond laser pulses [17][18][19].…”

Polarization Simultons in Stimulated Raman Scattering by Polaritons

“…One of the promising applications of solitons is, of course, spectroscopy. The comparative investigation of characteristics of spontaneous and stimulated Raman scattering (SRS) in different alkali-earth tungstate and molybdate crystals at both high and low-frequency anionic group vibrations was presented, for example, in [10]. It has been found that, among these crystals, the SrMoO 4 and SrWO 4 crystals are the most perspectives for SRS generation on both stretching and bending modes of internal anionic group vibrations with the strongest SRS pulse shortening under synchronous laser pumping.…”