Yellow Laser Raman Miniaturization Passively Q Cavity Frequency Doubling Crystals

The yellow-orange lasers with the spectral region from500nm and600nm are of interest for many applications in information storage, medicine, visual display, military, atmospheric sensing, DNA sequencing, and communications and so on But they are hardly obtained by frequency doubling Nd-doped lasers, because Nd-doped lasers could not operation efficiently in the spectral range of1120nm～1200nm.With Nd doped～1.06μm lasers and SRS in Raman crystal, the1.18urn first Stokes wavelength can be generated, and are intracavity frequency-doubled afterwards to generate the yellow laser～590nm. In recent years, the all-solid-state crystal Ramal lasers attract intensive research interests in the field of solid-state laser and nonlinear optics for the advantages of compaciness, high stability and high efficiency.SRS possesses many attractive features, i. e. no need for phase matching, beam clean-up, high brightness, good coherence, pulse compression, and high converdion efficiency. In addition, SRS operates with a Raman threshold, that is, only when the fundamental light intensity or power density exceeds a certain level, can the stimulated Raman scattering operates. Generally the Q-switched technology is used to achieve high peak power with narrow pulse width in tens of nanoseconds and even nanosecond, to achieve efficient stimulated Raman scattering frequency conversion. Compared with actively Q-switched techniques that employ acousto-optic or electro-optic modulators, passively Q-switched techniques use an intracavity saturable absorber that requires no external driving devices, and therefore have the advantages of simplicity, compactness and low cost.At present, there are a fewer reports about the yellow light by passively Q-switched crystal Raman yellow laser.Firstly, the characteristics of the Raman laser output from a diode-pumped passively Q-switched Nd:GdVO4crystal self-Raman laser and Nd:YVO4crystal self-Raman laser are investigated. Self-Raman laser, in which the laser medium is also the Raman medium, that is, a piece of crystal complete both stimulated emission process and the stimulated Raman scattering process, have many advantages of small-scale, compact, small intracavity lost and low threshold. The maximum Raman laser output at1176nm is520mW and the maximum conversion efficiency is10.3%in the experiment. Up to now, we report the highest Raman output power and the highest diode-to-Raman optical conversion efficiency obtained by LD pumped passively Q-switched Nd:GdVO4self-Raman lasers.Secondly, the characteristics of the Raman laser output from a diode-pumped passively Q-switched Nd:YAG/SrWC>4crystal Raman laser are investigated. Compared with self-Raman laser, it owns lower thermal lens effects and is easier to be optimized. When the incident pump power is6.3W, the obtained average output power at1180nm is800mW and the corresponding conversion efficiency from diode pump to Raman laser is12.7%, which is the highest diode-to-Raman optical conversion efficiency obtained by LD pumped passively Q-switched intracavity Raman lasers.At last, we theoretically and experimentally investigate the characteristics of LD pumped passively Q-switched intracavity frequency-doubled yellow Raman lasers, in which KTP crystal is used as the frequency-doubling crystal, and theoretical optimization is taken out to achieve the high yellow laser conversion for the passively Q-switched Nd:YAG/SrWO4/KTP/Cr.YAG yellow Raman laser. LD pumped passively Q-switched KTP intracavity frequency-doubled Nd:YAG/SrWO4yellow Raman laser is realized. When the incident pump power is6.6W, the obtained average output power at590nm is383mW and the corresponding conversion efficiency from diode pump to yellow laser is5.8%. Based on our experimental conditions, the space-dependent rate equations of passively Q-switched intracavity frequency-doubled Raman lasers are solved numerically, and groups of general curves are obtained to investigate the influence of the radius of curvature of input mirror, intracavity instinct losses for the fundermental laser, intracavity instinct losses for the first Stokes laser, initial transmission of the saturable absorber, the ratio of the length of Raman crystal to the optical length of the resonant cavity and the ratio of the length of frequency-doubling crystal to the optical length of the resonant cavity on the yellow laser performance, and theoretical optimization of the six parameters is taken out...