Design And Implementation Of A Passively Q-Switched/Mode-Locked Solid-State Laser Based On Titanium Aluminum Carbide Material

Generally,solid-state lasers have the characteristics of good monochromaticity,good directionality,good coherence,and high brightness.In recent years,pulsed solid-state lasers working at 2-μm waveband have been widely used in surgery,weather monitoring,material processing,optical frequency conversion,and other fields because of their unique advantages.The passively Q-switched(PQS)technique and passively mode-locked(PML)technique are important methods to obtain ultrashort pulsed lasers.In this thesis,a thulium-doped yttrium aluminate(Tm:YAP)crystal was used as the gain medium of the pulsed solid-state laser,and a saturable absorber which was prepared by using a material of titanium aluminum carbide was adopted as the optical modulator of the pulsed solid-state laser,and the output characteristics of the PQS and PML Tm:YAP laser were deeply researched,respectively.Firstly,the titanium aluminum carbide-based saturable absorber was prepared by using a method of ultrasonic-assisted liquid phase exfoliation and spin-coating technique,and the titanium aluminum carbide-based saturable absorber was characterized by using a Raman spectroscopy analyzer and an X-ray diffractometer.To verify the nonlinear optical properties of the titanium aluminum carbide-based saturable absorber,it was analyzed by using a self-assembled experimental equipment.The experimental results showed that the modulation depth,non-saturable absorption,and saturation intensity of the titanium aluminum carbide-based saturable absorber were calculated to be 4.74%,8.14%,0.14 MW/cm~2,respectively.Secondly,the basic principles of the PQS technique was introduced,and a Tm:YAP laser which had a straight laser resonant cavity structure with a titanium aluminum carbide-based saturable absorber was designed and operated in the PQS mode.The experimental results showed that choosing an output mirror with transmittance(T)of 1.5%for the experimental research,when the pump power was23.41 W,a maximum average output power of 2.01 W with a narrowest pulse width of 266.00 ns at 130.19 k Hz was achieved from the PQS Tm:YAP laser,corresponding to a slope efficiency of 10.64%.The center wavelength of the PQS Tm:YAP laser was 1988.86 nm.In addition,the beam quality factors M ~2 of the PQS Tm:YAP laser in the x direction and y direction are 1.04,1.08,respectively.Finally,the basic principles of the PML technique was introduced,and a PML Tm:YAP laser which had a standard Z-folded laser resonant cavity structure with a titanium aluminum carbide-based saturable absorber was designed and operated in the continuous-wave mode-locked(CWML)regime.The experimental results showed that choosing an output mirror with T of 1.5%for the experimental research,when the pump power was 23.90 W,a maximum average output power of 1.11 W with a shortest pulse width of 221.60 ps at 106.70 MHz was achieved form the CWML Tm:YAP laser,corresponding to a slope efficiency of 5.43%.The center wavelength of the CWML Tm:YAP was 1937.76 nm.In addition,the signal-to-noise ratio of the pulsed output signal from the CWML Tm:YAP laser was measured to be about 63 dB.