Study On The Technology Of Mode-Locked Tm:LuAG Laser

2?m wavelength laser,due to its wavelength characteristics,belongs to the bands of eye-safe and atmospheric windows.Meanwhile,water has strong absorption peaks around 2?m.Therefore,in the field of medical treatment,communication,environmental monitoring and so on,increasing attention have been paid to 2?m lasers together with relevant applications.Since its narrow pulse width and high peak power characteristics,ultrashort pulse laser has essential applications in biological cutting and optoelectronic device processing.This paper combines both above to main research which uses active mode-locked technology to obtain the active mode-locked pulse laser of Tm:LuAG crystal.First,this paper analyzes the development of mode-locked laser and Tm:LuAG crystal laser as well as physical and chemical properties of Tm:LuAG crystal.According to the spectral properties,788nm-output pump source is selected as the experimental pump.Through the energy structure of Tm3+ ion,the rate equation of Tm:LuAG crystal laser is obtained.With discussing the influences of Tm3+ ion concentration on the relaxation oscillation and up-conversion effect from the rate equation,threshold of the Tm:LuAG crystal laser is analyzed.Besides,the thermal effect of Tm:LuAG crystal is analyzed,including theoretical calculation and experimental measurement towards thermal focal length of the crystal,which illustrates that the strong thermal effect of crystal will have an impact on the output of the laser.It is necessary to select reasonable resonant cavity parameters to suppress the thermal effect.Secondly,we explained the principle of active mode locking,including the analysis of time domain and frequency domain,the principle of phase modulation and amplitude modulation,the analysis of pulse width without mismatch.We also introduced the design principle of mode locking resonator cavity.We obtained theoretical value of each parameter by the analysis of the influence of various parameters on the resonant cavity.Then we determined the specific structure of the resonant cavity.According to the resonant cavity structure obtained by simulation,the experimental device is set up and the laser output under continuous operation is obtained.Through research and debugging of the acousto-optic mode-locked modulator,the length of the experimental cavity is matched with the parameters of the crystal and mode-locked modulator,and the mode-locked pulse laser is obtained.The F-P etalons are added into resonant cavity to select wavelengths,which is able to obtain a more optimized mode-locked pulse laser output.Finally,the optical characteristics and wavelength pulse width of the output pulse laser are tested.Spectrum analysis is performed as well.The output of this mode-locked pulse laser has a central wavelength of 2023.75 nm,a maximum output power of 0.248 m W,a pulse width of 706 ps,a repetition frequency of 81.996 MHz and a beam quality as follow: M2=1.035.