V.A. Lisinetskii

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.

Efficient high-energy Raman laser for troposphere ozone lidar

Summary form only given. The use of a folded cavity for Raman laser to obtain the efficient high-energy first Stokes generation is demonstrated in this report. Four types of cavities (linear cavity, two types of folded three-mirror cavities and folded four-mirror cavity) are investigated. Optical pulses with 15-16 ns duration and 0.6 mrad divergence are generated at pump pulse energy up to 135 mJ. The obtained first Stokes pulses are frequency doubled in DKDP crystal to produce 281 nm radiation needed as an online radiation for different absorption lidars for ozone sounding in troposphere.

Pulse Dynamics of Raman Microchip-Lasers

Summary form only given. Pulse dynamics of passive Q-switched solid-state microchips - lasers and microchips - lasers with intracavity Raman conversion is investigated experimentally and theoretically. It is shown, that intracavity Raman conversion in microchips -lasers is a simple and effective method of generation of short pulses and peak power up to several tens of kW. At the fundamental wavelength microchips, lasers generate subnanosecond pulses with energy about several muJ.

2 kW threshold quasi-cw narrowband all-solid-state Raman laser generating in UV, visible and near IR ranges for spectroscopy

This contribution reports on experimental study of a barium nitrate based Raman laser system pumped with the second harmonic of a quasi-cw Nd:YAG laser. Five Stokes components generated and frequency doubled cover a spectral range of 280-740 nm with an average power from 10 to 800 mW and a spectral width of 0.2 cm in the visible range. Pulsed lasers generating tunable or multiwave radiation have wide applications in Raman spectroscopy. For the successful use, the developed lasers should meet such requirements as continuous tunability or multiwave operation in a wide spectral range, narrow linewidth, sufficient output power, low divergence of the laser beam, simplicity in operation and low cost. All-solid state lasers meet these requirements rather well. Especially Raman lasers using stimulated Raman scattering (SRS) of light in crystals can be promising laser sources for the spectroscopic applications. Recently, we have developed a cheap and simple Raman laser based on the wellknown barium nitrate crystal which can generate nanosecond narrowband (0.25 cm in IR) continuously tunable radiation in the ranges of 190-1800 nm [1,2]. The repetition rate of this laser was equal to 10 Hz. However, for many applications in spectroscopy, especially in Raman spectroscopy, it is necessary to use laser pulses with higher repetition rates, so-called quasi-cw radiation. High repetition rate can substantially improve the conditions of measurement of Raman spectra and shorten the time for this measurement. Recently, some studies have been performed to develop quasi-cw Raman lasers generating radiation in IR and visible ranges [3-6]. In these studies, comparatively high cost diode-pumped Raman lasers were used. To develop a cheap quasi-cw Raman laser and to extend the spectral range of its generation to UV region we have performed our studies on a barium nitrate based Raman laser system pumped with the second harmonic (SH) radiation of quasi-cw flash-lamp-pumped Nd:YAG laser and on frequency shift of Raman laser radiation using the second harmonic generation (SHG). The results of these studies are presented in this report. The optical scheme of the developed laser source is shown in Fig. 1. For pumping the Raman laser the linear polarized SH radiation at 532 nm from a commercially available quasi-cw (1 kHz) Nd:YAG laser with acousto-optic modulation (model LF2210, SOLAR TII) was used. The pumping pulse width was equal to 110 ns (FWHM). The pumping laser beam passed through an optical isolator (half-wave plate, polarizer and quarter-wave plate) to block back-scattered radiation or smoothly change the pump beam power and its polarisation between linear and circular and then the beam was focused with a lens inside a Raman laser resonator. The Raman laser consisted of two spherical mirrors and a barium nitrate crystal of 70 mm length between them. Spherical mirrors were used to compensate partly the thermal lens effect in the crystal due to the dissipation of Raman excitation to heat. Also, the crystal was mounted in a special cage for axial symmetric heat removing. Our previous studies using two-beam time-resolved z-scan in barium nitrate showed that a considerable thermal lens is induced in it due to SRS of nanosecond laser pulses [7]. Using z-scan data and measurement with the help of a collimated He-Ne laser beam propagating through a Raman laser we could determine the optical power of the thermal lens at 1