| Mid-infrared laser has important applications in various fields related to national economy and people’s livelihood.With the development of 2 μm laser technology,developing application-oriented mid-infrared lasers has become one of the important research directions in the international laser field.Exploring the potential laser transition process of activated ions beyond the conventional laser band,studying its regulation mechanism and realizing laser operation is an important means to obtain new infrared laser.The 3F4→3H6 transitions with emission wavelengths of 2 μm(1.9-2.1 μm)in Tm3+level transitions are the most studied stimulated radiation processes in recent years.In addition,Tm3+has other transitions,in which the transition of 3H4→3H5(4f3-4f3)is just at the 2.3μm band,which provides a technical means to expand the new band laser.The development of practical laser media and the resolution of related scientific issues are the material foundation for the development of new wavelength lasers.Exploring the structure-effect relationship between their laser effects and laser media is expected to provide reference value for breaking through the bottleneck of laser development.This thesis focuses on exploring the key mechanisms that affect the performance of 2.3 μm solid state lasers doped with Tm3+gain media,and explores the effects of doping concentration,output mirror transmittance,resonator length and other factors in different laser media on the gain competition effect,We have achieved 2.3 μm laser operation in Tm:YAP and Tm:YAG crystals,and achieved 2 and 2.3 μm dual wavelength operation,respectively,enriching the output wavelength of 2.3 μm band Tm3+doped solid state lasers.Finally,the output characteristics of 2 μm and 2.3 μm passively Q-switched pulsed lasers were studied using a new type of two-dimensional nanomaterials,providing a basis for expanding their applications in the field of nonlinear optics.The research content of this paper is summarized as follows:1.The research significance and application value of 2.3 μm laser is introduced,the laser emission mechanism of doped Tm3+laser system is analyzed,and the development history and research status of Tm3+solid laser are summarized.Finally,the ultrafast pulse generation technology combined with new two-dimensional nanomaterials is introduced in detail.2.The 2.3 μm laser transition mechanism of a LD pumped 2 at.%Tm:Y2O3 transparent ceramic laser was investigated.Without successfully outputting 2.3 μm laser light,its 2 μm output characteristics were studied,and a 2μm continuous laser operation with a slope efficiency of 7.9%and 1.7 W was obtained.The suppression effect of gain competition mechanism on 2.3 μm laser oscillation is analyzed,and a reasonable scheme for optimizing the doping concentration of the substrate is proposed.3.The effects of different doping concentrations on the output power of Tm3+YAP 2.3μm CW laser is studied by adjusting the intracavity loss of laser resonator.Among them,2.3 μm single wavelength output 2.4 W was obtained at 2 at.%concentration.Dual-wavelength laser output of 3.8 W and 2.3 μm laser output of 2.98 W were obtained at 3 at.%concentration.The optimum doping concentration is 3 at.%.Secondly,the effects of different output mirrors on dual-wavelength 3 at.%Tm:YAP lasers are studied.The ETU effect is used to explain the phenomenon that gain competition is alleviated,and the output power and oblique efficiency of 2.3 μm laser are improved.A series of parameters such as effective nonlinear absorption coefficient-16cm/MW,saturation light intensity 1.18 MW/cm2,modulation depth 17%and so on were determined.The passive Q-switching of the SA using the easily integrated MoS2 thin film was achieved with 228 kHz,316 ns and output power of 398 mW.It is proved that the prepared thin film has great optical nonlinearity and good uniformity,and is a potential 2.3 μm solid state laser modulator.4.The effect of doping concentration on the operation of Tm:YAG 2.3 μm laser is investigated.A single wavelength output with power 1.49W and oblique efficiency of 10.1%is obtained by reasonable planning of resonator length and cavity loss.Subsequently,dualwavelength operation was realized in 2 at.%Tm:YAG.However,the effect was greatly reduced,and the output power was only 220 mW.This phenomenon was explained reasonably.Finally,the characteristics of the Tm:YAG crystal 2.3 μm pulsed laser were studied by using the largesized MoS2 thin film,and the pulse laser of up to 150 ns and 190 KHz was obtained.It is proved that the new type of saturable absorber based on MoS2 can be used as a substitute for Cr2+:ZnSe to produce shorter Q-switched pulse output. |
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