Research Of Laser Frequency Conversion Based On RTP And KTA Crystal

The Optical parametric oscillation(OPO)and stimulated Raman scattering(SRS)are very important nonlinear frequency conversion techniques,through their frequency conversion,we can get new type of laser output which can not be obtained by the ordinary laser.The laser diode(LD)pumped all solid intra-cavity OPO and Raman lasers have the advantages of low threshold,compact structure and high conversion efficiency,which attracts more and more people's attention.RTP and KTA crystals are isomorph with KTP crystal,which have high efficiency second-order nonlinear optical effect,and the strong Raman gain,they are the outstanding frequency conversion crystals.This paper based on the two kinds of crystals in the optical parametric oscillation and Raman laser were researched,respectively.In this paper the main research contents are as follows:1.The intra-cavity OPO laser is researched which are based on the LD end pumped Nd:YAP/RTP.The RTP crystal is used as the nonlinear frequency conversion crystal of intra-cavity OPO which is cut by the non-critical phase matching(?=900,?=00)and the size is 4×4×20mm3.At the pump power of 13.1W and pulse repetition frequency of 20 k Hz,1.65?m eye safety laser is obtained with the average output power of 1.1W,the efficiency of the pump light into signal light is 8.4%,the narrowest pulse width is 4.4 ns,the highest single pulse peak power of30.8 k W under the pulse repetition frequency is 5 k Hz.2.The Raman laser is researched which are based on the LD end pumped Nd:YAG/KTA.The KTA crystal is chosen as the intra-cavityRaman frequency conversion crystal,the Raman effect of KTA crystal is studied and analyzed.KTA Raman crystal is cut with the X axis and two different size of the KTA are studied(the size is 5×5×25mm3 and5×5×20mm3,respectively).The KTA Raman crystal with the length of25 mm,the maximum average output power of 1.12 W is obtained under the pump power of 10.9W with the pulse repetition frequency of 15 k Hz,the efficiency of the pump light into Raman laser is 10.3%,the pulse width of 7.6 ns and slope efficiency was 15.2%.More than one stokes spectrum of light are observed,the wavelengths of 1091 nm,112nm,1150 nm and 1182 nm are corresponding KTA crystal 234cm-1 frequency shift of the first-order,second-order,third-order and fourth-order stokes line,respectively.The 1147 nm is corresponding KTA crystal 671cm-1first-order stokes line frequency shift.