Self-Raman Lasers Emitting New Wavelengths

Stimulated Raman scattering (SRS) is a three order nonlinear-optical effect. Solid state Raman lasers enrich the spectra of lasers using SRS principle. The wavelength of the Raman laser is determined by the wavelength of the pump source and the Raman shift of the Raman gain medium. In theory, every pump wavelength can generate one corresponding new wavelength through SRS conversion. Solid state Raman lasers have important applications in areas such as industrial production, national defense and scientific research.Self-Raman laser crystals are both Raman active and laser active, the invention and employment of which makes solid state Raman lasers much more compact and less expensive. Nd:YVO4crystal is one of important self-Raman crystals. It can generate several fundamental laser lines at1064nm,1066nm,914nm,1342nm and so on. Its high Raman gain near the Raman shift of890cm-1has drawn people’s continuous attention and the self-Raman lasers using890cm-1Raman shift have been fully investigated in recent years. Nd:YVO4crystal has some other Raman shift peaks (for example259cm-1) with which new wavelengths could be generated. Nd:KLu(WO4)2crystal is a good laser crystal and the KLu(WO4)2crystal is Raman active, however no self-Raman laser based on Nd:KLu(WO4)2crystal has been reported.This thesis focuses on two new wavelengths of self-Raman lasers. One is1097nm by using Nd:YVO4crystal at259cm-1Raman shift. The other is1185nm by using Nd:KLu(WO4)2crystal at907cm-1Raman shift. This thesis systematically studied the output laser characteristics of actively and passively Q-switched c-cut Nd:YVO4self-Raman laser at the wavelength of1097nm. Then the second harmonic laser was generated by frequency doubling of1097nm self-Raman laser using LBO crystal. This thesis then studied the laser characteristics of the Nd:KLu(WO4)2crystal. The Nd:KLu(WO4)2self-Raman laser pumped by xenon lamp was achieved for the first time and the influence elements on the self-Raman laser characteristics were analyzed.The main content of this thesis is as follows1. The actively Q-switched c-cut Nd:YVO4intracavity self-Raman laser was achieved with the808nm LD as the pump source and an acousto-optic modulator as the Q-switch. The output power and pulse energies of the Stokes laser were investigated versus the pump power and pulse repetition frequencies. The fine spectrum and typical pulse of the stokes laser were recorded and analyzed.2. The passively Q-switched c-cut Nd:YVO4intracavity self-Raman laser was achieved with the808nm LD as the pump source and an Cr:YAG crystal as the saturable absorber. The output power, pulse repetition rate and pulse width of the Stokes laser were investigated versus the pump power. The fine spectrum and typical pulse of the Raman laser were recorded and analyzed.3. The actively Q-switched c-cut Nd:YVO4intracavity frequency-doubled visible Raman laser was achieved with the808nm LD as the pump source and an acousto-optic modulator was used as the Q-switch. The visible Raman laser was generated by frequency doubling of1097nm self-Raman laser with an LBO crystal. The change of output power and spectrum versus the temperature of the LBO crystal was analyzed. The temperature for most efficient second harmonic conversion of1097nm laser was found out. The output power, pulse repetition rate and pulse width of the visible Raman laser were investigated versus the pump power. The fine spectrum and typical pulse of the Raman laser were recorded and analyzed.4. The laser characteristics of the Nd:KLu(WO4)2crystal were studied with xenon lamp as the pump source. The fundamental laser at the wavelength of1070nm and the second harmonic laser at the wavelength of535nm were achieved. The actively Q-switched intracavity self-Raman laser was realized. An electro-optic modulator (EO) was used as the Q-switch. The influence of the output mirror and the coupling mirror on the generation of self-Raman laser was investigated. The output power of the Stokes laser was investigated versus the pump voltage on the lamp. The spectrum of the Raman laser was analyzed and the pulse shape was recorded.