Research On All-Solid-State Tunable Laser Based On Crystal Birefringence

The tunable all-solid-state laser has a compact laser structure and eximious operating performance,which can be widely used in a series of fields like spectral analysis,multiplexed optical communication,laser range finder,integrated optics,laser medical treatment and so on.Over the years,the technology of Nd:YAG all-solid-state lasers operating at wavelengths above 900 nm have become increasingly mature.However,there is still a gap in the laser wavelength expansion below 900 nm,which possesses crucial scientific research value because of its applications in environmental monitoring,lidar,atmospheric communication and a seed source for indirect blue lasers used in highdensity data storage and cell counting.Especially tunable Nd:YAG all-solid-state lasers at wavelength of lower than 900 nm are rarely studied.In this thesis,an experimental scheme of lower wavelength tunable Nd:YAG all-solid-state laser based on crystal birefringence is proposed.A three-level Nd:YAG single-wavelength discrete tunable laser at 869 nm(pure three-level),875 nm(quasi-three-level)and 878 nm(quasi-three-level)was performed in experiment.Among the three wavelengths,the maximum output power of 1.21 W of 869 nm laser was achieved.In addition,a simultaneous continuouswave(CW)dual-wavelength Nd:YAG laser at 875 nm and 878 nm was realized for the first time,and the maximum output power of 875 nm and 878 nm was measured respectively as 0.48 W and 0.62 W when the absorption pump power of the simultaneous continuous-wave dual-wavelength Nd:YAG laser reached 18.6 W,The following is an introduction about main research contents of this thesis :(1)The compositions and working properties of the diode-pumped all-solid-state Nd:YAG laser are presented.The possibility of laser wavelength of a quasi or pure threelevel Nd:YAG laser is analyzed according to the energy level and the spectral of Nd:YAG crystal.(2)This thesis expounds the operating principle of the birefringent filter.Using optical cavity eigen equation and round-trip Jones matrix method,the transmission characteristics of birefringent filter is deduced.The feasibility of tunable lower wavelength laser obtained by birefringent filter and resonator to suppress strong radiation spectrum line and the non-target spectral lines is discussed.(3)Experimental demonstration of single-wavelength discrete tunable laser based on crystal birefringence of 869 nm,875 nm and 878 nm laser output was achieved,it can be tuned between the three wavelengths.The influences on the laser output caused by the variation of absorption pump power and output transmittance were also studied.(4)Experimental demonstration of the continuous-wave(CW)simultaneous dualwavelength laser based on crystal birefringence with wavelength at 875 nm and 878 nm was realized.The dual wavelength stability of the laser and the effect on output power generated with a change in the absorption pump power were also studied.In conclusion,the derivation,the analysis and the experimental research of a tunable all-solid-state laser based on birefringent filter are presented detailedly in this thesis.The tunable all-solid-state lasers including a single-wavelength tunable three-level Nd:YAG laser at three wavelengths of 869 and 875 and 878 nm as well as a continuous-wave simultaneous dual-wavelength laser with operating wavelength at 875 and 878 nm were obtained.The research in this thesis provides a new idea for the realization of lower wavelength laser by using crystal birefringence and resonator to suppress the non-target emission lines.