Investigation On Nd:YVO₄ Self-raman Laser And Optical Frequency Conversion

Stimulated Raman scattering is an important method to obtain new-wavelength lasers,and it has become a research hotspot in the field of laser.By using a cascade Raman method,the laser output wavelength can be extended which enrich the new wavelength.In addition,visible-band laser can be obtained by combining the Raman scattering effect and the second order nonlinear frequency conversion technique.It has important applications in laser medical,display and other fields.Nd:YVO₄ crystal is an outstanding self-Raman crystal with excellent laser and Raman properties.In this thesis,cascaded self-Raman operations were demonstrated in a-and c-cut Nd:YVO₄ crystals,respectively.And frequency doubling,sum frequency and OPO were realized in second-order nonlinear optical crystals pumped by second Stokes line at 1176nm.The main contents of this thesis are listed as follows.1.Stokes lasers with different wavelengths were obtained in Nd:YVO₄ crystals with different cutting directions based on different Raman shifts.Wavelengths around 1.1-1.2?m were achieved with the Raman shift of 259cm^-11 in a c-cut Nd:YVO₄ crystal.The influence of the parameters on the critical pump power of cavity instability,including focus position of pump light in the crystal,pulse repetition rates and duty cycle of Q-switch,have been experimentally.By optimizing these parameters,average output power of 1W was achieved at the pump power of 14.9W and the pulse repetition rate of 15kHz.In addition,wavelengths at 1.2-1.3?m were achieved based on cascaded conversion with the Raman shifts of 259 and 890cm^-1.A maximum output power up to 1.02W was achieved at the pump power of 17.1W and the pulse repetition rate of10kHz,corresponding to the conversion efficiency and the slope efficiency were 6.0%and 9.1%,respectively.Further more,a diode-end-pumped second-Stokes self-Raman laser at 1313nm was demonstrated in an a-cut Nd:YVO₄ crystal,with the primary Raman shift of 890cm^-1.A maximum output power up to 2.5W was obtained,corresponding to the conversion efficiency and slope efficiency were14.7%and 23.7%,respectively.The wavelengths based on Raman shifts of 259 and 890cm^-11 enrich the output wavelength of Nd:YVO₄self-Raman.2.Sum frequency and OPO were achieved derived by Nd:YVO₄self-Raman laser.Based on the temperature phase matching technology,588nm yellow laser and 559nm green laser were obtained in a LBO crystal.When the pulse repetition rate was 60kHz,the output power of2.5W at 588nm and 1.8W at 559nm were obtained at the temperature of314K and 362K,respectively.In addition,an intracavity OPO emitting at1.7?m pumped by Nd:YVO₄ self-Raman laser is demonstrated with a KTA crystal used as nonline optial crystal.The OPO conversion from1064nm to 1.5?m was suppressed and the OPO conversion from 1176nm to 1.7?m was achieved.The output power of 1.2W was achieved at the pump power of 12.1W and the pulse width of 2ns,corresponding to a conversion efficiency of 10%.