A.S. Grabtchikov

All solid-state diode-pumped Raman laser with self-frequency conversion

Operation of an all solid-state compact pulsed Raman laser pumped by a continuous-wave laser diode is demonstrated. The Stokes and anti-Stokes radiations of stimulated Raman scattering at the 1.181 and 0.973 μm wavelengths, respectively, are generated as a result of self-frequency conversion of the 1.067 μm laser radiation in a Nd3+:KGd(WO4)2 crystal. With Q-switched operation, the Raman laser threshold corresponds to 230 mW of a laser diode light power. The output power of 4.8 mW is achieved at the Stokes wavelength with a kilohertz repetition rate.

Continuous-wave Raman generation in a diode-pumped Nd 3+ :KGd(WO 4 ) 2 laser

Continuous-wave Raman generation in a compact solid-state laser system pumped by a multimode diode laser is demonstrated. The Stokes radiation of stimulated Raman scattering at 1.181 microm is generated as a result of self-frequency conversion of the 1.067 microm laser radiation in Nd3+:KGd(WO4)2 crystal placed in the cavity. The Raman threshold was measured at 1.15 W of laser diode power. The highest output power obtained at the Stokes wavelength was 54 mW. The anomalous delay of Raman generation relative to the start of laser generation (the oscillation buildup) due to slow accumulation of Stokes photons in the cavity at low Raman gain and Raman threshold dependence not only on the laser intensity but also on the time of laser action are observed.

Multimode pumped continuous-wave solid-state Raman laser

We demonstrate the continuous-wave operation of a solid-state Raman laser containing a barium nitrate crystal as the Raman medium. The Raman laser, which has a singly resonant cavity, is pumped by multimode radiation. The Raman oscillation threshold is reached at approximately 2 W of pump power. As much as 500 kW/cm2 of Stokes power density at 60-kW/cm2 pump power density is obtained in the cavity.

Efficient diode-pumped passively Q-switched laser operation around 1.9 μm and self-frequency Raman conversion of Tm-doped KY(WO4)2

Passively Q-switched operation of Yb,Tm:KY(WO4)2 and Tm:KY(WO4)2 lasers diode pumped at 805 nm has been investigated. A thin plate of Cr:ZnS was used as a saturable absorber for passive Q switching. A maximum average output power of 116 mW emitted at 1.9 μm in comparison to 160 mW for the free-running regime at the same pumping level has been obtained with a slope efficiency of 26% with respect to the incident pump power. Using a Tm:KYW sample with broadband antireflection coatings and dichroic laser resonator mirror, the first Stokes component of Raman self-frequency conversion was observed at 2365 nm.

Observation of Raman conversion for 70-fs pulses in KGd(WO4)2 crystal in the regime of impulsive stimulated Raman scattering.

Raman conversion of femtosecond pulses in a solid-state medium is reported. Stimulated Raman scattering (SRS) was observed in an impulsive SRS regime when the pump pulses duration was comparable with the period of Raman-active vibration. The generation of super broadband radiation, which is a distinguishing feature of impulsive SRS, is shown.

Bessel beam transformation by anisotropic crystals

Transformation of Bessel beams by biaxial and uniaxial crystals is investigated experimentally and theoretically. Experimental observations show beam symmetry changing and formation of complex intensity patterns, depending on the orientation of the crystal. These patterns can appear as a regular system of peak intensities. Results of numerical calculations support the experimental findings.

Two-Stokes generation and effect of multiwave mixing on output pulse parameters of a Q-switched Raman microchip laser

The two-Stokes generation of a Q-switched microchip laser with intracavity stimulated Raman scattering frequency conversion and multiwave mixing has been investigated theoretically and experimentally. The dependences of the output power and the pulse repetition rate of the Nd:LaSc3(BO4)3 (Nd:LSB)-Cr:YAG-BaWO4 microchip laser on the pump power have been experimentally obtained and the shapes of the fundamental, first Stokes, and second Stokes pulses have been recorded. The effect of the intracavity multiwave mixing on the characteristics of the both Stokes pulses and their shapes has been analyzed. The modeling of the output parameters and the calculated pulse shapes agree well with the obtained experimental results.

Generation of sum frequency mixing radiation at cw intracavity Raman conversion

Recent obtaining continuous-wave (cw) Raman conversion in solid-state laser system [1] opens perspectives for creation of new cw laser sources at new wavelengths by means of further nonlinear conversion. Thus, intracavity frequency-doubled cw crystalline Raman laser was reported lately [2]. This report presents first data on investigation of intracavity sum-frequency generation in diode pumped solid state laser on Nd:YVO4 with self frequency Raman conversion.

Spectral shift of Raman generation band in a Bessel pump beam

A spectral shift in the first Stokes generation band has been observed at stimulated Raman scattering in a Bessel light beam. Under nanosecond pulse excitation in barium nitrate crystal, the Stokes emission propagating along the Bessel beam axis has been found to be frequency shifted toward the blue side by 3.7 GHz with respect to the Stokes emission propagating along the surface of a cone. Numerical data have shown that the observed frequency shift is directly related to the contribution of the real part of the Raman susceptibility to the refractive index. This contribution causes an increase in the Stokes gain out of exact Raman resonance owing to induced focusing, which inhibits diffraction spread of generated light and thus provides its better spatial overlap with the pump beam.

Continuous-Wave Crystalline Raman Lasers

Continuous- wave generation of Ba(NO3)2 Raman laser pumped by multimode argon laser and diode pumped Nd:KGW and Nd:YVO4 lasers with Raman conversion is investigated. Output Stokes power and generation efficiency reached 160 mW and 5%.