We present a highly efficient ring-cavity all-solid-state BaWO Raman laser generating at both the long-shift (ν=925  cm) and short-shift (ν=332  cm) Raman lines under external picosecond synchronous pumping at the wavelength of 1063 nm. Very high slope efficiencies and output pulse energies of 68.8% and 103 nJ at the ν-shifted Stokes wavelength of 1179 nm, and 38.6% and 53 nJ at the (ν+ν)-shifted Stokes wavelength of 1227 nm have been achieved. Self-mode locking of the (ν+ν)-shifted Stokes field under intracavity pumping by the ν-shifted Stokes field allowed to realize 12-fold shortening of the 1227 nm radiation pulse down to 3 ps close to the shorter dephasing time of the ν Raman line at the output pulse peak power 1.5 times higher than the pump peak power.

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Abstract:A quasi-continuously pumped picosecond oscillator-amplifier laser system based on two identical 2.4% Nd:YAG slabs in a single bounce geometry was developed and investigated. The oscillator was passively mode locked by the multiple quantum well saturable absorber inserted into the resonator in transmission mode. Output train containing 7 pulses with total energy of 900 μJ was generated directly from the oscillator. Single pulse with energy of 75 μJ, duration of 113 ps and Gaussian spatial profile was cavity dumped from the resonator and amplified by the single pass amplifier to the energy of 830 μJ. Comparison with our previously reported data obtained with similar system based on Nd:GdVO4 shows advantage of using highly doped Nd:YAG for generation of sub-millijoule pulses in one hundred picoseconds range, which might be interesting in many applications. Schematic of the laser oscillator and amplifier

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.

Use of a Tm:YAP laser (wavelength 1998 nm, power 1 W, irradiance 14 W/cm(2), interacting time 60 sec) which is at the same time compact and small enough to be used in the dental practice, together with moderate cooling, could be an efficient tool for debracketing.