Study On 2-micron Single-longitudinal-mode Ho:YVO₄ Laser And Amplifier

The region of 2μm is widely used in medicine,photoelectric countermeasure and material processing,due to its advantages of being in a region which belongs to eye-safe range and atmospheric window.In particular,2μm single-longitudinal-mode laser has the advantages of stable frequency,narrow linewidth and so on.The2μm single-longitudinal-mode solid-state laser has application prospects in the fields of Optical Parametric Oscillator,Coherent Doppler Wind Lidar and so on.In this thesis,for the purpose to enrich the way of producing and amplifying 2μm single-longitudinal-mode laser,single-longitudinal-mode continuous-wave（CW）Ho:YVO₄ laser,single-longitudinal-mode pulsed Ho:YVO₄laser and single-longitudinal-mode pulsed Ho:YVO₄ amplifier are studied theoretically and experimentally.This paper firstly introduces the investigation progress of 2μm single-longitudinal-mode solid-state laser and amplifier.The investigation progress of 2μm single-longitudinal-mode solid-state lasers with different doping ions and different matrix materials is analyzed.The characteristics of the technical means to realize 2μm single-longitudinal-mode CW solid-state laser and 2μm single-longitudinal-mode pulsed solid-state laser are analyzed,and the investigation progress is summarized.The advantages of using Ho-doped vanadate crystal as gain medium to realize 2μm single-longitudinal-mode CW laser output by unidirectional ring cavity structure and 2μm single-longitudinal-mode pulse laser output by inserting passively Q-switched element into unidirectional ring cavity are analyzed.The investigation progress of 2μm Ho-doped vanadate single-longitudinal-mode MOPA amplifier is introduced.The feasibility of single-longitudinal-mode pulsed Ho:YVO₄ laser power amplification using MOPA structure is analyzed.The investigation progress of Cr²⁺:Zn S-based passively Q-switched 2μm solid-state laser and graphene-based passively Q-switched 2μm solid-state laser is introduced.The advantages of using Cr²⁺:Zn S and graphene to achieve passively Q-switched operation are analyzed.The theory of single-longitudinal-mode CW Ho:YVO₄ laser is analyzed in detail.The temperature distribution in Ho:YVO₄ crystal is calculated,and the thermal effect of Ho:YVO₄ crystal is analyzed.The rate equations of the single-longitudinal-mode CW Ho:YVO₄ laser are established,and the influence of different parameters on the output performance of the single-longitudinal-mode CW Ho:YVO₄ laser is discussed.This provides a reference for the experimental study of single-longitudinal-mode CW Ho:YVO₄ laser.The stability of single-longitudinal-mode CW Ho:YVO₄ laser cavity is analyzed by ABCD matrix theory,and the waist radii of the oscillating light at different positions in the cavity are calculated.The single-longitudinal-mode CW Ho:YVO₄ laser is studied experimentally.The output characteristics of 1.94μm all-fiber Tm-fiber laser are analyzed,and the feasibility of 1.94μm all-fiber Tm-fiber laser as the pump source of single-longitudinal-mode CW Ho:YVO₄ laser is analyzed.A 37.8 W Tm:YAP solid-state microlaser with low relaxation oscillation is designed and realized,and the feasibility of using it as the pump source of single-longitudinal-mode CW Ho:YVO₄laser is analyzed.The principle of single-longitudinal-mode laser with unidirectional ring cavity based on isolator is introduced.A 1.10 W,2.0529μm single-longitudinal-mode CW Ho:YVO₄ laser using an isolator and a half wave plate pumped by 1.94μm all-fiber Tm-fiber laser was designed and realized.The performances of single-longitudinal-mode CW Ho:YVO₄ laser and single-longitudinal-mode CW Ho:Gd VO₄ laser are compared.The passively Q-switched single-longitudinal-mode Ho:YVO₄ laser by using ring cavity structure is studied theoretically and experimentally.Theoretically,the rate equations of passively Q-switched laser with unidirectional operation are established.The influence of different parameters on the pulse width and other characteristics of single-longitudinal-mode pulsed Ho:YVO₄ laser is analyzed.A Cr²⁺:Zn S-based passively Q-switched single-longitudinal-mode Ho:YVO₄ laser with average output power of 1.02 W,central wavelength of 2.0530μm,repetition rate of67 k Hz and pulse width of 910 ns was realized.A graphene-based passively Q-switched single-longitudinal-mode Ho:YVO₄ laser with average output power of1.06 W,central wavelength of 2.0529μm,repetition rate of 93 k Hz and pulse width of 1332 ns was realized.Two kinds of single-longitudinal-mode pulsed Ho:YVO₄ power amplifiers are studied theoretically and experimentally.Theoretically,the laser output characteristics of single-longitudinal-mode pulsed Ho:YVO₄ residual pump amplifier and single-longitudinal-mode pulsed Ho:YVO₄ two-stage power amplifier are analyzed.Experimentally,A single-longitudinal-mode pulsed Ho:YVO₄ residual pump power amplifier with an average output power of 1.67 W and a magnification of 1.64 times is realized by using the residual pump laser of the seed laser as the pump laser of the amplifier.Using a two-stage MOPA structure,a 10.8 W single-longitudinal-mode pulsed Ho:YVO₄ two-stage power amplifier is realized.The average power of the single-longitudinal-mode pulsed seed laser is amplified by an order of magnitude.