Research Of Dual-wavelength Narrow Line-wideth All-solid-state Laser Based On Intra-cavity Pumping Technolog

Narrow line-width dual wavelength laser has a very broad application prospect in laser medical treatment,lidar monitoring,gravitational wave detection and other frontier scientific research fields.At present,the main method to obtain dual-wavelength laser is a single gain medium,and there is gain competition between the transition spectral lines,which leads to a series of problems such as low output power and low conversion efficiency,and it is difficult to achieve stable narrow line-width dual-wavelength laser output simultaneously.In view of this phenomenon,this paper proposes a technical scheme based on intra-cavity pumping technology and F-P etalon.In this scheme,the gain competition between the transition lines can be avoided fundamentally,because the 0.9?m quasi-three-level laser and the 1.0?m four-level laser are generated in their respective gain media.On this basis,the F-P etalon is introduced to increase different losses for each longitudinal mode in the cavity,to suppress the oscillations of other modes except the central mode,and the line-widths of two laser beams can be compressed simultaneously.In addition,in order to analyze the optical?mode characteristic and stability of the resonator more intuitively,this paper innovatively introduces the propagation circle theory into the resonator design of the intra-cavity pumping dual-wavelength narrow line-width laser,the logical relationship between the propagation circle-transformation circle,the thermal lens focal length and dynamic stability of the intra-caivty pumping dual-wavelength narrow line-width laser resonator is established.On this basis,the influence of resonator parameters on the mode characteristics and output characteristics of the intra-caivty pumping dual-wavelength narrow line-width laser is analyzed and optimized more intuitively.In the aspect of theoretical research,the output power expression of the intra-cavity pumping dual-wavelength narrow line-width laser with reabsorption losses and F-P etalon losses and four-level laser high reflection mirror losses are established,the rate equations of quasi-three-level and four-level lasers with multiple losses are solved.By simulating the inversion population density of the intra-cavity pumping dual-wavelength narrow line-width laser,the photon density,inversion population density and the output power with the F-P etalon are obtained.The effect of the rotation angle of the F-P etalon on the output characteristics of the intra-cavity pumping dual-wavelength narrow line-width laser with reabsorption losses is obtained.The theoretical results shows that with the change of vertical placement angle of F-P etalon,the variation trend of four-level laser output power is more obvious than that of quasi-three-level laser.In the aspect of experimental research,the stable output of the intra-cavity pumping dual-wavelength laser is firstly studied.When the pumping power is 9.6W(the central wavelength of pump source is 808nm),the output power of the quasi-three-level laser at 912 nm is reached,and the independent oscillation of quasi-three-level laser is obtained.When the pumping power reaches 17 W,the four-level laser begins to oscillate,and with the increase of pumping power,the output power of the four-level laser increases with the increase of the quasi-three-level laser.When the maximum pumping power is 38.8W,the dual-wavelength laser output of 3.6W is obtained.The output power of the quasi-three-level laser at 912 nm is 1.4W,and the output power of the four-level laser is 2.2W,the conversion efficiency is 9.3% and the oblique efficiency is 17.1%.When the pumping power reaches 30 W,the transverse mode of the dual-wavelength laser is measured with approximate gaussian distribution,and the symmetry is good.The M~2 values of 912 nm and 1064 nm lasers are 1.35 and 1.28,respectively.It shows that the dual wavelength laser output with better beam quality can be obtained by using the intra-cavity pumping technology.Then,the stable output of the intra-cavity pumping dual-wavelength narrow line-width laser is studied.On the basis of stable output of dual-wavelength laser,the F-P etalon is introduced in the cavity,and the line-width compression of dual-wavelength laser is realized simultaneously.In the narrow line-width dual-wavelength laser experiment,when the pumping power is 32.48 W and the rotation angle of F-P etalon is 15°,the minimum wavelength line-width of the two laser beams is obtained,corresponding 0.284 nm and 0.627 nm,respectively,and the number of two laser beam longitudinal modes is 2.The output power of 912 nm is 17 mW,the output power of 1064 nm is 16 mW,and the conversion efficiency is 0.1%.When the rotation angle of F-P etalon is 10°,the maximum output power at 912 nm is 107 mW and the maximum output power at 1064 nm is 35 mW,the maximum conversion efficiency is 0.44%,and corresponding line-width is 0.501 nm and 0.905 nm,respectively.The experiment results shows that: when the vertical placement angle of F-P etalon is changed,the variation trend of the four-level laser output power is more obvious than that of the quasi-three-level laser.By comparing the experimental results with the theoretical results,it can be seen that the experimental results are in good agreement with the theoretical results.The output power of dual-wavelength laser shows a variation tendency of “from high to low” to “from low to high”.The paper describes the theoretical model of the intra-cavity pumping dual-wavelength narrow line-width laser,which can reasonably describe and explain the internal operation process of the intra-cavity pumping dual-wavelength narrow line-width laser.