Study On Multi-wavelength Pumped High Beam Quality Nd:YAG Pulsed Laser

Laser ranging has the advantages of high measurement accuracy,fast speed,and non-contact measurement.It is an efficient and accurate ranging technology and is widely used in industrial manufacturing,construction measurement,aerospace,military defense and other fields.With the development of technology,the core component solid-state laser needs to be miniaturized,and the multi-wavelength laser diode pumping technology can effectively reduce the volume.In this paper,the multi-wavelength laser diode-pumped solid-state laser is aimed at producing stable high output energy and high beam quality.Using the variable reflectivity Gaussian mirror to suppress the edge diffraction of the resonator,a multi-wavelength laser with a Gaussian mirror as the output coupling mirror is designed.Wavelength-pumped plano-convex unstable and concave-convex stable cavity solid-state lasers.First of all,the theoretical analysis of the multi-wavelength pump laser resonator:based on"gain medium,pump source,and resonator",the gain medium part,the physical characteristics of different gain media are compared in detail,and Nd:YAG crystal with better performance is selected;For the pumping source part,compare the characteristics of the traditional lamp pumping source and the laser diode pumping source,select the laser diode with high pumping efficiency as the pumping source,and use ANSYS to simulate the gain medium thermally,and use MATLAB to analyze the thermal lens effect of the crystal;The resonant cavity part is introduced by the structural parameters of the resonant cavity,and the relationship between the cavity parameters and the laser output light parameters is established according to the light transmission matrix of the Gaussian beam.stability.Secondly,analyze the output characteristics of multi-wavelength LD side-pumped Nd:YAG lasers,starting from the energy level structure and absorption lines of Nd:YAG crystals,establish and solve the Nd:YAG rate equation;characteristics,establish and solve the active Q-switching rate equation.And use MATLAB to simulate the photon number density and inversion particle number density in the cavity to reflect the output characteristics of the laser.Finally,the emission wavelength of the pump source at different temperatures was tested by a spectrometer.According to the absorption line of the pump light by the Nd:YAG crystal,the optimal operating temperature of the pump source is 30°C.The output characteristics of the flat-convex unstable cavity and the concave-convex dynamic stable cavity pumped by side pulses of multi-wavelength LDAs are compared experimentally.Under the conditions of pumping current 150 A,repetition frequency 30 Hz,and pumping pulse width,the flat-convex unstable cavity outputs a laser with a single pulse output energy of 176 m J and a pulse width of 4.8 ns,and the beam quality along the x-axis and y-axis are respectivelyM_x~2(28)3.1andM_y~2(28)3.2;the concave-convex dynamic stable cavity outputs a single pulse output energy of 160 m J,the laser pulse width is 7.5 ns,the beam quality along the x-axis and along the y-axis are respectivelyM_x~2(28)3.0andM_y~2(28)4.6;in the stability test,the flat-convex unstable cavity has no The average energy is 144 m J when the temperature is controlled and controlled,the average energy is 131 m J when the temperature is controlled by the concave-convex dynamic stability chamber,and the average energy is 135 m J when there is no temperature control.According to the known literature,the output energy of 176 m J is the maximum energy of the currently known multi-wavelength pumped solid-state laser at a repetition rate of 30 Hz,and when there is no temperature control(24°C-49.5°C),it can output an average energy of 144 mJ of laser light.