Studies Of New Solid-state Lasers Based On Nonlinear Optical Effect

The research of this thesis is divided into two parts:one part is the study of solid-state lasers based on nonlinear effect,and the other part is the research of a new Nd:GdLuAG laser.In the first part,the main focus is on nonlinear optics,including optical frequency doubling,stimulated Brillouin scattering and stimulated Raman scattering,combining with flash lamp pump and LD pump,the engineering assembly of 1064&532 nm flash-lamp-pump lasers and the continuous-wave external Raman laser are studied respectively.As an important component and research object in laser field,solid-state lasers play a great role in scientific research and laser applications.In traditional solid-state lasers,pulsed flash-lamp-pump lasers,because of their high peak power and pulse energy,extraordinary output energy,are widely used in laser drilling,cutting and other industrial processing.Although the semiconductor laser diode(LD)developed later than flash-lamp-pump lasers,in the 80's,the huge development of LD greatly promote the development of solid-state lasers.Today,high-power LD pumped solid-state lasers have important applications in military,scientific,communications,medical and other fields.The application of nonlinear optical effect has greatly expanded the field of application of solid-state lasers.Through specific nonlinear optical processes,such as frequency doubling,optical parametric oscillation,stimulated Raman scattering and so on,the wavelength of laser has covered the range from ultraviolet to IR or even terahertz wave,which satisfies the need of different practical applications.At the same time,another nonlinear optical effect:stimulated Brillouin scattering(SBS)is also widely concerned because of pulse width compression effect.As a kind of human eye safety laser,1.4 ?m lasers have played a great role in remote sensing,medical and communication fields.The 1.4 ?m lasers are usually obtained by taking Nd:YAG as gain medium,due to its excellent physical and chemical properties,scientists have studied it carefully.The performance of Nd:GdLuAG,as a new crystal,in 1.4 ?m has not been explored.In this thesis,using Nd:YAG crystal as gain medium,the 1064 and 532nm pulse laser is obtained,and the engineering prototype is completed on the basis of the native production device.The single longitudinal mode laser is obtained on the basis of flash-lamp-pump laser,and the pulse width compression experiment is carried out based on stimulated Brillouin scattering effect.The output characteristics of 1443.9nm laser in continuous and passively Q-switched state are studied through LD end-pumped with a new mixed crystal Nd:GdLuAG.At the same time,the theoretical threshold of the continuous Raman laser is studied,and the improvement scheme is came up according to the problems in experiments.This article mainly carries on the following several aspects research:1.Using Xenon lamp pump Nd:YAG crystal,at 10Hz pump frequency,through the electro-optic Q-Switched method,the 1064nm pulse laser is obtained,with the pulse width of 7.2 ns.Because of the design of the unstable cavity,the divergence angle of the laser is 0.75 mrad.The maximum energy of 1064 nm laser can reach 1 J.After the use of KTP crystals as a frequency doubling crystal,the 532 nm pulse laser is achieved,with the maximum output energy of 500 mJ.By utilizing fully localized devices,such as Gaussian mirrors,dual-lamp pump cavity,electro-optic Q-switched devices,etc.,completed the assembly of the engineering prototype,The laser parameters of the laser are comparable to those of the professional photoelectric company in the market.2.Using Xenon lamp pump Nd:YAG crystal,at 1 Hz repetition,by designing the twisted mode cavity,using the F-P etalon as the output mirror,inserting the Cr:YAG crystal in the cavity,the small energy single longitudinal mode 1064nm laser is obtained,with the pulse width of 20 ns,and the energy is 8 mJ.Theinterference fringes of 1064 nm laser are measured by the method of Fabry PerotInterferometer,which can be seen clearly.Then we utilize the obtained single longitudinal mode laser to carry on the experiment of pulse width compression based on SBS,because of the single-longitudinal output instability,the pulse width compression phenomenon is not obvious.According to the experiment result,we propose the follow-up plan:using the self-seed injection method to raise the single longitudinal mode occurrence probability and the line width of single-longitudinal mode laser to obtain the ideal pulse width compression.3.The output characteristics of 1443.9 nm laser of LD end-pumped Nd:GdLuAG crystal were studied.Using 808 nm LD laser as pump source,the maximum output power of 1.36 W is achieved under continuous wave(CW)operation with the optical to optical conversion efficiency of 11.9%.By taking V3+:YAG as saturated absorber,the passive Q-switched laser output is obtained,with the maximum output power of 164 mW and the corresponding single pulse energy of 29.3 ?J.4.The theoretical thresholds and experimental feasibility of CW external Ba:W04 Raman lasers are studied.Firstly,the cavity mirror transmittance of the Raman outer cavity is theoretically analyzed,and the theoretical values of the Raman threshold and beam waist of the pump and Raman laser are obtained by establishing the threshold formula of the CW external Raman laser.In the experiment,the Raman resonator is constructed according to the theoretical value,but the Raman laser output is not obtained because of the experimental cavity design.In view of the causes of this result,an improved scheme is proposed for the subsequent experiments.The innovation of this thesis is mainly as follows:1.With the use of fully localized devices,such as electro-optical Q-switched devices,dual-lamp pump cavity,etc.,we completed the 1064&532 nm laser engineering prototype assembly.The output characteristics of the laser can be compared with Beamtech Optronics Company's laser performance,while their devices are more imported products.2.Using Nd:GdLuAG crystal as gain medium,the 1443.9 nm laser output characteristics under CW and passively Q-switched operation are investigated by LD pump.The maximum output power that can be achieved in the continuous operation is 1.36 W,and the maximum output power under the passive Q-switched state is 164 mW.This is the first time to utilize Nd:GdLuAG crystal to obtain 1443.9 nm lasers.3.The feasibility of using Ba:WO4 crystals as Raman media to obtain a CW external Raman laser is studied.In theory,the selection of the transmittance of Raman resonator cavity mirrors is discussed,and the threshold formula of the CW Raman laser is built,and the theoretical values of the Raman laser threshold and beam waist of the pump and the Stokes laser are simulated.This is the first theoretical study of the CW external Raman laser by taking Ba:WO4 as Raman crystal.