| The development and application of ultrafast pulsed laser is a very important frontier field in modern science and technology.Especially,the emergence of femtosecond laser techniques provides a novel technical route for the exploration of the natural world.The ultrafast pulsed laser with high peak power and ultra-wide spectrum has important applications in various fields such as military,industrial,scientific research,communications,environmental,medical and extreme physical condition simulation.Saturable absorber is one of the core devices of pulsed laser,however,the fabrication technology of trandition semiconductor saturable absorption mirror(SESAM)is complicated,expensive and the absorption bandwidth is narrow,which greatly limits the application range of SESAM.Since graphene has been successfully applied to pulsed lasers,research on the saturation absorption characteristics of graphene-like two-dimensional(2D)layered materials(eg,transition metal sulfides,black phosphorus,topological insulators)has attracted intense attention.Constrained by quantum confinement effect,the physical properties of.layered TMDs were different from bulk materials.A large number of studies have proved that the lattice arrangement,stoichiometric ratio and thickness all have a significant effect on phase information,energy band structure,carrier absorption and ultrafast relaxation process.The bundant structure and properties make it have broad prospects in optoelectrincs devices application.However,the saturable absorption effect of instrict TMDs mateirals is relatively weak and the adjustment of modulation parameters is difficult.It is necessary to adopt some other modification methods for two-dimensional materials to effectively enhance their saturation absorption parameters such as modulation depth and saturation intensity.A greater degree of regulation,while further broadens the optical absorption bandwidth of TMDs,to better meet the requirements of different laser parameters.In view of the disadvantages of two-dimensional TMDs optical modulator in pulsed lasers,embarked on the exploration of new materials and new technologies with the preparation of lower cost,simpler growth process,stronger nonlinear saturation absorption effect,and wider bandwidth.We systematically analyzed the saturable absorption properties of TMDs with different phases.Through alloying and informing heterostructure structure make optical modulation properties of the TMDs materials in pulsed lasers enhanced.The TMD-based compostion was applied in all-solid-state ultrafast pulsed lasers and we obtained the high-power femtosecond lasers.The study is of great scientific significance and application value in exploring the novel optoelectronic modulator devices and promoting the development of all-solid-state ultrafast pulsed laser technology.The main research contents and significant results are as follows:1.The WS2 and MoS2 film semiconductor were fabricated by thermal decomponsition method.Combined with the open-aperture Z-scan and I-scan technique,the saturable absorption characteristics were systematically studied.Theoretically,we analyzied the saturable absorption mechanism of TMDs.Experimentally,with WS2 and MoS2 saturable absorber,the passively Q-switched pulsed lasers with the performance of 1.11 MHz/57.96 ns and 0.71 MHz/155.4 ns were successfully realized.(In chapter 2)2.We systematically explored the theoretical band structure and optical properties including anisotropy,linear optical absorption and saturable absorption of metal 3R phase NbS2.The optical absorption process and the SA mechanism were theoretically discussed.Based on the 3R-NbS2 saturable absorption mirror fabricated by liquid phase exfoliation,we successfully achieved the nanosecond and femtosecond pulsed laser with Nd:GdVO4 and Yb:KYW crystal,respectively.(In chapter 3)3.We investigated the saturable absorption properties of three kinds of alloys including the MoSSe consist of different types of anions,MoWSe2 consist of different types of cations in the same family and NbMoSe2 consist of different types of cations in the different family.Based on first-principles calculations,the relation between element ratio and the carrier transport and optical properties of alloy was systematically studied,especially in nonlinear optical characteristics.With ternary alloy as optical modulator,the nanosecond pulsed laser in all-solid-state laser was built.We studied the effects of alloy with different element ratio on pulsed laser performance.Moreover,the femtosecond mode-locked Yb:KYW laser based on MoSSe was realized firstly.(In chapter 4)4.We combined the semiconductor MoS2 and semimetal graphene,forming the van der Walls vertical heterostructure G/MoS2.Theoretically,the work function of G/MoS2 versus MoS2 thickness was calculated and the carrier transport process was analyzed.Using the open aperture Z-scan,I-scan and pump-probe techniques,we systematically explored the nonlinear optical response and carrier dynamics of G/MoS2.Compared with graphene and MoS2,the SA effect of G/MoS2 was greatly enhanced and carrier relaxation process was accelerated.Based on G/MoS2 saturable absorber,we firstly achieved the femtosecond solid-state pulsed laser to the best of our knowledge.The TMDs saturable absorption mirror(SAM)was replaced by a SESAM,and the results were compared with that of mode-locked laser based on TMD SAM.(In chapter 5)... |
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