Study On The Nonlinear Optical Properties Of Alloyed Transitional Metal Dichalcogenides

Due to the strong coherence of electrons,two-dimensional materials have excellent optical,electrical,and chemical properties,and have attracted much attention in the fields of energy storage,catalysis,optoelectronics,and nonlinear optics.In recent years,two-dimensional materials have drawn much attention due to their excellent nonlinear absorption characteristics.Due to their excellent properties,transitional metal dichalcogenides(TMDCs)play an important role as saturated absorbers(SA).TMDCs own a large advantage in saturated absorption properties.In order to optimum and adjustable application performance,efforts have been made to explore new two-dimensional TMDCs with composition changes,such as alloyed TMDCs.These novel alloyed TMDCs have some unique properties compared to binary TMDCs.Therefore they have great potential applications with enhanced performance such as nonlinear optics,electronics/optoelectronics,catalysis,sensors,biomedical,energy storage.In this paper,alloyed TMDCs are prepared by Chemical Vapor Transport and applied to the field of nonlinear optics.We study the nonlinear optical properties of WS1.76Te0.24,WSe1.4Te0.6 and Mo0.53W0.47Te2 alloys.The main research contents of this paper include:(1)The saturable absorber models are theoretically studied,and the relationship between the transmittance of the saturable absorber and the excitation intensity is obtained.It is possible to combine z-scan technique to obtain parameters of important parameters such as modulation depth,saturation intensity,nonlinear optical absorption coefficient ?NL,third-order nonlinear optics Im?3,and figure of merit(FOM).The two-temperature model of pump-probe technology is studied.Based on the pump-probe system,the relaxation time of the alloyed materials can be obtained.(2)The saturation light intensity and modulation depth of WS1.76Teo.24 SA at 1060 nm are lower and deeper than the WS2 and WTe2 saturated absorbers.The stable Q-switched Yb:GSAO laser based on WS1.76Te0.24 saturable absorber is obtained.Compared to the WS2 and WTe2 saturable absorbers,the WS1.76Te0.24 saturable absorber operates at the narrower pulse width of 230 ns.Based on the pump-probe system,the relaxation time of WS1.76Te0.24 nanoflakes is 3.8 ps,indicating that the material can be applied to ultra-fast lasers.(3)The broadband saturated absorption characteristic of WSe1.4Te0.6 is obtained.The saturation light intensity and modulation depth of WSe1.4Te0.6 SA at 0.6 ?m,1.0?m and 2 ?m are lower and deeper than the WSe2 and WTe2 saturated absorbers.The stable Q-switched lasers at 639nm,1059nm and 2?m are built.The narrower pulse widths of the WSe1.4Te0.6 saturable absorbers are 302ns,556ns and 1.289?s,respectively,which is narrower than the WSe2 and WTe2 saturable absorbers.Thus alloyed WSe1.4Te0.6 is a good saturated absorber.Based on the pump-probe system,the relaxation time of nanoflakes is 0.28 ps.(4)The ultrawide saturation absorption characteristics of Mo0.53W0.47Te2 nanoflakes are obtained at wavelengths of 0.6 ?m,1.0 pm,2 ?m,3.0 ?m and 4.0 ?m.Also,the Mo0.53W0.47Te2 exhibits a higher modulation depth and a lower saturation light intensity at 0.6 ?m,1.0 ?m,2 pm than the 2H-MoTe2 saturated absorber.Based on the pump-probe system,the ultrafast relaxation time of Mo0.53W0.47Te2 is 10ps.