The Study On Saturable Absorption Characteristics Of Transition Metal Dichalcogenides And Its Application In Mid-Infrared Lasers

All-solid-state mid-infrared lasers have been widely used in many fields,such as biomedical,military defense,laser manufacturing,atmospheric detection,space communication and so on.The emergence of new two-dimensional saturable materials brings new opportunities for the development of laser modulation.Q-switching pulse laser technology is one of the common methods to obtain narrow pulse width and high peak power.First-principle calculation is a method for calculating a series of basic properties of the system in many fields such as physics,materials and so onIn this thesis,the saturable absorption mechanism of MoSe2,MoTe-2,WSe2 and WTe2 has been investigated by using VASP(Vienna ab initio simulation package)software package.The layered MoSe2,MoTe2,WTe2,WSe2 and MoWS2 nanosheets were produced by ultrasonic-assisted liquid exfoliation method.Structure morphology and saturable absorption characteristics of layered nanosheets were characterized.Q-switched Ho.Pr:LiLuF4,Er:Lu2O3 and Er:YAG lasers with home-made transition metal dichalcogenides(TMD)saturable absorbers(SAs)at 2.95 ?m.2.85 ?m and 1.6?m were researched,respectively.The research contents of this thesis are as follows:1.Based on density functional theory(DFT),the saturable absorption mechanism of MoSe2,MoTe2,WSe2 and WTe2 has been investigated by using VASP.2.The layered MoSe2,MoTe2,WTe2,WSe2 and MoWS2 nanosheets were produced by ultrasonic-assisted liquid exfoliation method.The MoSe2.MoTe2,WTe2,WSe2 and MoWS2 SAs were fabricated with YAG substrates3,The morphology of the as-prepared SAs was characterized by using transmission electron microscopy(TEM)and atomic force microscopy(AFM).Absorption spectrum and nonlinear transmission were measured4.Passively Q-switched Ho.Pr:LiLuF4 laser at 2.95 ?m was achieved based on MoSe2.MoTe2 and WTe2 SAs.With WTe2-SA,a pulse width of 366 ns and a repetition rate of 92 kHz were obtained5.Passively Q-switched Er:Lu2O3 laser at 2.85 ?m was achieved based on WSe2-SAs.A maximum output power of 776 mW was obtained with a pulse duration of 280 ns at a repetition rate of 121 kHz,producing a pulse energy of 6.4 ?J and a peak power of 21.3 W.6.Passively Q-switched Er:YAG laser at 1645 nm was achieved based on MoWS2-SAs.A maximum output power of 1.62 W was obtained with a pulse duration of 1 ?s at a repetition rate of 43 kHz.producing a pulse energy of 37.7 ?J and a peak power of 37.7 W.