Two-dimensional Layered Transition Metal Dichalcogenides Based Optical Modulators And The Study Of Their Nonlinear Properties

As one of typically two-dimensional(2D)layered materials,semiconductor transitionmetal dichalcogenides(STMDCs)own remarkable physical behaviors.Recently,researchers have explored that STMDCs could be used as one of distinct optical modulation materials.Furthermore,since STMDCs based optical modulators have broadband modulation ability,strong interaction between materials and light as well as high third-order nonlinear susceptibility,those excellent properties mean that STMDCs could be employed as ideal saturable absorption devices in pulsed fiber laser systems to transferring continues-wave into stable pulse trains output.In this thesis,we mainly focus on the study of nonlinear optical properties of 2D-STMDCs and their applications as saturable absorbers(SAs)in fiber laser systems.In chapter two,we mainly introduce four common processes to prepare STMDCs films and the main characterization methods.Additionally,there is a detail introduction for the possible mechanisms of nonlinear saturable absorption properties of STMDCs and several structure types of STMDCs based SA devices.In chapter three,we mainly introduce the process of preparing STMDCs based endreflective all-fiber integrated SA devices using magnetron sputtering deposition technique(MSD),and achieving passively Q-switched pulse trains.After further optimizing the design of our devices,we deposit the WS2 film on the tip of a Panda-style polarization maintaining fiber(PMF)by employing MSD.Via incorporating our SAs into an Erbium-doped linear fiber laser system,we obtain passive Q-switching operation with high stability and signal-to-noise ratio.We compare the Q-switched output performances under different cavity parameters and obtain the optimized parameters for laser cavity engineering.In addition,we prepare a WS2-MoS2-WS2 heterostructure based SA,combined with distinctly nonlinear saturable absorption properties of heterostructures,we achieve the passively mode-locking operation with 296 fs pulse duration in experiment.In chapter four,we mainly introduce the few-layer WS2 and MoSe2 grown by chemical vapor deposition(CVD)technique.Incorporating with related characterization methods,we demonstrate that the few-layer WS2 and MoSe2 grown by CVD technique own large areas and high crystal quality.In our experiment,we prepare few-layer WS2 and MoSe2 based SA devices,respectively.Then we study their nonlinear saturable absorption properties systematically.Via embedding them into Erbium-doped fiber laser systems,we obtain passively Q-switched and mode-locked pulse trains with great output laser performances,respectively.In final chapter,we conclude the mainly experimental results in our thesis.Then we analyze and discuss the current experimental project where it needed to be optimized in the following work.Finally,we outlook to the development of our work in the future and look forward to further improving the performances of our SA devices and experimental results.