Study On Preparation And Ultrafast Properties Of Saturable Absorber Based On Two Dimensional Topological Materials

In the course of the development of saturable absorber(SA),the discovery of graphene provides a valuable clue for the future research direction.The rapid development of graphene has attracted much attention.Two dimensional topological materials such as transition metal chalcogenides(Transition two Metal Dichalcogenides TMDs)is a kind of typical graphite based materials,in electrical and mechanical,optical and thermal direction and so many advantages,it is widely used in various fields.In this paper,we study the characteristic of the ultra short pulse generated by a two-dimensional topological material as saturable absorber.The generation of ultra short pulse is usually realized by adjusting the Q technology and the mode locking technique,in which the passive Q and passive mode locking techniques are commonly used because of their simple structure and good stability.As an indispensable component of the saturable absorber,SA has been the focus of researchers.From the initial dye saturable absorber,saturable absorption mirror(SESAM),then to carbon nanotubes,graphenei,until now the two-dimensional topological material,SA has experienced a long history of development,the generation of ultrashort pulse technology is in progress.The main contents of this paper are:1.The research background of the subject and the research significance and the preparation method of the two dimensional topological materials are discussed,and the research progress of the passively Q-switched performances or saturable absorber is summarized.2.Preparation of Molybdenum Disulfide(MoS2)was studied.We also use them in Q-switched and Q-switched mode-locked lasers.The performance of passively Q-switched and Nd:GYSGG laser operating with MoS2 as the saturable absorber was demonstrated.The maximum dual-wavelength average output power of 250 mW was achieved under the absorbed pump power of 4 W,corresponding to the optical-to-optical conversion and slope efficiency of 6.5%.The minimum pulse width was 833 ns with the pulse repetition rate of51 kHz.Passively Q-switched mode-locked dual-wavelength Nd:GYSGG laser using MoS2 saturable absorber is demonstrated.At the pump power of 4 W,the maximumaverage output power of 0.167 W was obtained with the optical conversion efficiency of3.96 %.The mode-locked pulse inside the Q-switched envelope has a repetition rate of 78 MHz and its pulse width is estimated to be about 260 ps.3.Preparation of tungsten disulfide(WS2)was studied.We also use them in Q-switched and Q-switched mode-locked lasers.We demonstrate WS2 based saturable absorber for passively Q-switched Nd:GYSGG laser.Using WS2 as saturable absorber,stable Q-switching operation was obtained with the shortest pulses are 620 ns and 591 ns,respectively,the corresponding repetition rate is about 67.35 kHz and 70.7 kHz,the optical conversion efficiency is about 9.2% and 7.5%,respectively under the pump power of 4 W,When the output mirrors are respectively of 15% and 27%.Passively Q-switched mode locking performance of Nd:GYSGG crystal using WS2 as saturable absorber was demonstrated.The maximum average output power of 0.153 W was obtained with the optical conversion efficiency of 3.22%.The shortest pulse width is 307 ps,the repetition rate is 78 kHz.4.Preparation of antimony telluride(Sb2Te3)was studied.We also use them in Q-switched laser.Passively Q-switched mode-locked dual-wavelength Nd:YVO4 laser using Sb2Te3 saturable absorber is demonstrated.At the pump power of 2.3 W,the maximum average output power of 0.119 W was obtained with the optical conversion efficiency of 3.79 %.The mode-locked pulse inside the Q-switched envelope has a repetition rate of 93.85 MHz and its pulse width is estimated to be about 925 ps.