Research On All-solid-state High Repetition High Polarization Master Oscillator Power Amplifier

The high-repetition,high-polarization 1064nm all-solid-state laser has a wide range of applications in the fields of laser ranging,photoelectric countermeasures,and laser fine processing.When the pump power of the traditional all-solid-state laser(DPSSL)increases,the crystal is affected by the heating effect and the depolarization effect,which leads to the deterioration of the beam quality factor and the decrease of the degree of polarization,which limits the output power of the laser.The main oscillating stage-power amplifier stage(MOPA)structure is an effective means to achieve high power,high repetition frequency,and high polarization all-solid-state laser output.In response to this problem,this article conducts experimental research on the all-solid-state high-repetition-frequency and high-polarization MOPA laser.In this thesis,acousto-optic Q-switched and passively Q-switched Nd:YVO₄ lasers are used as the local oscillator stage,and LD end-pumped Nd:YVO₄ is selected as the amplification stage to achieve high repetition frequency and high polarization laser output.The paper reviews the research status of high-repetition frequency and high-polarization MOPA structure lasers at home and abroad,and introduces the related theories of high-repetition frequency and high polarization MOPA structure lasers.Based on the theory of local oscillator level lasers,the LD end-pumped Nd:YVO₄ laser local oscillator level resonator structure is designed,and 7W high polarization laser output is realized in the free-running state,and the light-to-light conversion efficiency is 38.90%.Through the built-in acousto-optic Q-switching device in the cavity,at a repetition frequency of 90k Hz,4.9W high repetition frequency and high polarization laser output is realized,the light-to-optical conversion efficiency is 27.40%,and the pulse width is 89.60ns;at the repetition frequency of 10k Hz,the laser output power is 2.18W,and the pulse width is40.20ns.Using Cr⁴⁺:YAG passively Q-switched method,when the initial transmittance T is95.57%,the maximum output power is 2.21W.The pulse width is 67.60ns,and the repetition frequency is 144.36k Hz.Under the condition that the initial transmittance is approximately the same,the output characteristics of passively Q-switched lasers with single Cr⁴⁺:YAG crystal and double Cr⁴⁺:YAG crystals connected in series are comparatively studied,and the laser output with repetition frequency of 9.56k Hz and7.88k Hz is obtained,and the pulse width is respectively.They are 23.60ns and 21.80ns.The LD end-pumped Nd:YVO₄ laser amplifier is designed.In the 7W free-running state,the polarization laser output of 11.9W is obtained through single-stage single-end LD end-pumped amplification,and the energy extraction efficiency of the amplifier stage is27.44%.When the acousto-optic Q-switched repetition frequency is 90k Hz,the polarization laser output of 8.9W is realized through amplification,and the energy extraction efficiency of the amplification stage is 16.24%.In the case of passively Q-switched,single-stage LD single-ended pumping and single-stage LD double-ended pumping amplification are studied.The seed light with a power of 2.21W is amplified by a single-stage single-ended LD pump,4.2W high repetition frequency and high polarization are obtained.The laser output,the energy extraction efficiency of the amplifier stage is 7.07%.The 2.21W seed light is amplified by a single-stage double-ended LD pump to obtain a 4.8W high repetition frequency and high polarization laser output,and the energy extraction efficiency of the amplifier stage is 6.79%.