Theoretical Study Of LD End-pumped All-solid-state Continuous Wave Single-frequency Laser At 3μM

All-solid-state continuous-wave single-frequency lasers at 3μm have advantages of narrow linewidth,low noise,wavelength corresponding to atmospheric transmission window,a strong absorption band for biological components such as water molecules and hydroxyapatite,thus they have been widely applied in free space quantum information,nonlinear optics,biophotonics,laser medicine and trace gas detection.Especially in the generation of 8-12 μm tunable far-infrared laser,so the development of high-power narrow-linewidth all-solid-state continuous-wave single-frequency lasers at 3μm is imperative.Therefore,based on the all-solid-state laser technology,the theoretical study on the development of all-solid-state continuous-wave single-frequency 3 μm laser using LD end-pumped Er:YAG crystal has been elaborated in this thesis.The main study contents are as follows:1.The physical properties and spectral properties of Er:YAG crystal and the energy processes in Er:YAG laser were introduced in detail based on literature research.Then,the influence of crystal temperature on the properties of stimulated radiation cross section and energy level lifetime was analyzed through data fitting.After that,the mechanism of the thermal effect of Er:YAG crystal,the thermal lens effect of Er:YAG crystal and the change of thermal induced diffraction loss under thermal effect were analyzed theoretically.Finally,the parameters of four-mirrors ring cavity was designed based on reducing the thermal effect of the crystal.2.The theoretical model of the rate equation of the 3 μm laser system based on Er:YAG was established and the rate equations of the system was solved.According to the implicit function relationship between the input and output power,the influence of different laser parameters on the output behaviors of the continuous-wave single-frequency 3 μm laser was further analyzed.The laser parameters include the temperature and doping concentration and length of the laser crystal and cavity parameters.The cavity parameters include the transmission of the output coupler,the mode matching ratio between the oscillating and the pump laser and the one-way device insertion loss.According to the theoretical simulation results,the optimal temperature and doping concentration and length of the laser crystal,the transmission of the output coupler,the mode matching ratio between the oscillating and the pump laser,one-way device insertion loss were determined.