Research On The Characteristics Of The 2μm Solid-state Laser Based On The Disordered Structure Crystals

2μm laser is an eye-safe laser,and contains the absorption peaks of water and numerous gas molecules,which has important applications in the fields of medical surgery,gas detection,environmental monitoring,laser radar,material processing.In addition,2μm laser system can also be used as a pump source of mid-infrared and far-infrared laser systems to generate the laser of mid-infrared(3-5μm)and far-infrared(8-12μm)wavelength region.The wide application of 2μm laser has aroused strong concern among scientific researchers.In this paper,the characteristics of 2μm continue-wave,wavelength tunable,Q-switched,mode-locking,harmonic mode-locking and thermal lens effect are studied based on Tm3+doped and Tm3+,Ho3+co-doped crystals.Based on Tm3+:CNNGG crystal,a new method of measurement the thermal lens focal length by interferometric is investigated.By using a quartz birefringent filter as a wavelength tuning element,the wavelength tuning characteristics of Tm3+,Ho3+:GAGG crystal and Tm3+,Ho3+:CALGLO crystal are studied.By utilizing a graphene saturable absorbed mirror,the Q-switched Tm3+,Ho3+:GAGG laser is achieved.By using a SESAM,the mode-locking Tm3+,Ho3+:GAGG laser output characteristics is researched.Based on the Tm3+,Ho3+:CALGLO crystal,the harmonic mode-locking laser output characteristics is investigated.The specific content is summarized as follows:Ⅰ.Propose a method for online measuring the thermal lens effect of 2μm gain crystals.The reasons of the generation of the thermal lens effect is analyzed.And the generation of the interference rings under lasing and no-lasing condition is analyzed in detail during the experiment.Based on the radius of the interference rings the thermal lens focal length is calculated.Then the thermal lens focal length of the LD pumped Tm3+:CNNGG bulk laser in lasing and no-lasing operation is simulated theoretically.The thermal lens focal length simulated theoretically is basically consistent with the experimental results calculated by the interference rings.Ⅱ.The basic principle of the wavelength tuning in 2μm region by the quartz birefringent filter is analyzed.The continue-wave laser output characteristics of Tm3+,Ho3+:GAGG crystal and Tm3+,Ho3+:CALGLO crystal are investigated.With an OC of T=3%,the maximum output power of 448mW and 311mW are obtained respectively,corresponding to a slope efficiency of 13%and 6.6%.By using a quartz birefringent filter,the tunable laser properties of Tm3+,Ho3+:GAGG crystal and Tm3+,Ho3+:CALGLO crystal are studied,the tuning ranges of 77nm(2041nm-2118nm)and 130nm(1996nm-2126nm)are obtained respectively.Ⅲ.The basic operating principle of the Q-switched is analyzed.A graphene saturable absorbed mirror is prepared is prepared by the copper-based monolayer graphene transfer method.The growth process of the Tm3+,Ho3+:GAGG crystal by Czochralski method is represented.Using a graphene saturable absorbed mirror as the passively Q-switched element in a LD pumped Tm3+,Ho3+:GAGG laser,stable Q-switched operation is achieved.Stable Q-switched pulse train with a minimum pulse duration of 576.9ns is obtained,corresponding to an output wavelength of 2090.8nm and a repetition rate of 69.46KHz.Ⅳ.The method of generating 2μm mode-locking pulse and the principle of passive modelocking by SESAM are analyzed.By using a SESAM,the continue-wave mode-locking operation based on the Tm3+,Ho3+:GAGG crystal is realized.The characteristics of the mode-locking laser pulse under different transmittance OC and different intracavity group delay dispersion is investigated.With the OC of T=1%and intracavity group delay dispersion of 290fs2,a stable mode-locking pulse train with minimum pulse duration of 10.84ps is achieved,corresponding to a repetition rate of 83.01MHz and a maximum average output power of 33.17mW.V.The principle of harmonic mode-locking is analyzed.Based on the Tm3+,Ho3+:CALGLO crystal,the harmonic mode-locking operation is realized,the effect of different intracavity group delay dispersion on harmonic mode locked operation is investigated.With the introduced group delay dispersion of-4000fs2,mode-locking operation with repetition rate of 105MHz is firstly implemented.Next,a second order harmonic mode-locking pulse train with a repetition rate of 210MHz and a fourth order harmonic mode-locking pulse train with a repetition rate of 420MHz are obtained.With the introduced group delay dispersion of-2600fs2,mode-locking operation with repetition rate of 95.4MHz is achieved.Then a second order harmonic mode-locking pulse train with a repetition rate of 190.8MHz and an output power of 70mW is obtained by increasing the pump power.