Research On All-Solid-State Subnanosecond Laser

The subnanosecond solid-state laser is a solid-state laser with a pulse width of less than 1 ns,compared with the traditional laser,it has the advantages of narrower pulse width and higher peak power,has a wide application prospect in micro machining and manufacturing,laser medical treatment and diagnosis,nonlinear optics and other research fields.Its narrow pulse width and single longitudinal mode output can be used for high-precision ranging and three-dimensional imaging;its high peak power and high repetition frequency can be used for laser-induced spectroscopy and nonlinear optics;it can also get the subnanosecond 532nm green laser by frequency doubling.In the field of ocean exploration and underwater communication,the narrow pulse width green light is an important application light source due to the weak blue absorption of green light,especially in the definition of ablation aerosol number and chemical properties,the green laser pulse repetition rate and energy stability play a major role.Therefore,sub-nanosecond solid-state lasers with high pulse energy have important scientific research value.Based on the theoretical analysis and numerical simulation,the pulse output of pulse width 693ps and energy 102?J is obtained by using Nd:YAG/⁴⁺:YAG bonded crystal,and then by comparing the end pump and side pump amplification,the pulse output of3.8W is finally realized.The main research work of the paper is divided into four chapters.In the first chapter,the research background of subnanosecond solid-state lasers is introduced,and its application value is described in terms of laser ranging,laser induced breakdown spectroscopy,and environmental monitoring.The research status of subnanosecond solid-state lasers at home and abroad is summarized.Describes the main research content of this paper.In the second chapter,the⁴⁺:(4crystal was introduced from three aspects:spectral characteristics,energy level structure and saturated absorption characteristics.The operating mechanism of passive Q-switching is described,and the expressions of peak power,single pulse energy and pulse width of the output pulse are obtained by solving the passively Q-switched rate equations.The energy output expression of multipath amplification is obtained by using pulse amplification theory,which provides a theoretical basis for further experimental research.In the third chapter,the effects of cavity length,output mirror transmittance,and pumping mode on output pulse width were obtained by experiments on the separation of Nd:YAG and⁴⁺:(4.The best transmittance of the output mirror was found.Using Nd:YAG/⁴⁺:(4bonded crystal parameters,the curve of pulse width with cavity length and initial transmittance was analyzed,and the pulse with pulse width of693ps and output power of 102mW was finally obtained.The instability of the pulse is improved to some extent by compressing the duty cycle and reducing the coupling ratio.The polarization properties of⁴⁺:(4crystal were demonstrated by experiments.In the fourth chapter,the output power of the 888nm end pump Nd:YV₄ crystal double-pass amplification is simulated numerically.The effective absorption coefficient of Nd:YV₄ crystal to 888nm end pump and output power and optical-to-optical conversion efficiency of Nd:YV₄ crystal at 888nm end pump of short cavity are measured.The experiment finally obtained double-pass amplification output power of 1.3W.The two-way amplification power of side pump Nd:YAG crystal is calculated numerically.The short cavity output power and optical-to-optical conversion efficiency of the side pump Nd:YAG crystal are measured experimentally,and the thermal focal length is measured using an asymmetric steady cavity method of 400 mm.The two-way amplifier output power is finally 3.8W.