Saturable Absorption Of MoS₂ Under Vacancy Defects

In recent years,pulse laser has been widely used in the Internet of things and optical reuse.In order to meet the market demand,we carried out the research on the saturable absorption of MoS₂ under the introduction of vacancy defects,and effectively adjusted its performance,The main research contents and results are as follows:(1)For single-layer or double-layer MoS₂,vacancy defects are introduced to change the material into indirect band gap material.By introducing a vacancy defect of Mo atom,the band gap of single MoS₂ layer changes from 1.756 e V to 0.253 e V,and that of double MoS₂ layer changes from 1.269 e V to 0.267 e V.By introducing a vacancy defect of S atom,the band gap of single MoS₂ layer changes from 1.756 e V to 1.074 e V,and the band gap of double MoS₂ layer changes from 1.269 e V to 0.761 e V.The band gap of MoS₂ can be further reduced by changing the number of defects.Therefore,the introduction of vacancy defects in Mo atoms has a greater impact on the material band gap.(2)Vacancy defects affect the absorption properties of MoS₂.For single-layer MoS₂,the peak value of absorption coefficient decreased from 1.72×105 cm^-1 to 0.49×105 cm^-1(S atom)and 0.42×105 cm^-1(Mo atom);For double-layer MoS₂,the peak value of absorption coefficient decreased from 2.27×105 cm^-1 to 0.45×105 cm^-1(S atom)and 0.43×105 cm^-1(Mo atom),and the peak waveform of absorption coefficient widened.The effect of introducing vacancy defect of Mo atom is more obvious.Vacancy defects affect the reflection properties of MoS₂.For single MoS₂ layer,the peak reflectivity changes from 0.31to 0.23(S atom)and 0.17(Mo atom);For double MoS₂ layer,the peak reflectivity changes from 0.67 to 0.81(S atom and Mo atom).Due to the introduction of vacancy defects,the peak bandwidth of the reflectivity curve of MoS₂ increases gradually.In the long wavelength region,the curve rises obviously and is smoother.(3)With the increase of the number of vacancy defects,the wavelength shift of the peak value of absorption coefficient is not large.In the ultraviolet and visible band,the absorption coefficient of the peak value tends to be smaller,and the curve of absorption coefficient is very obvious in the range of 0.5×10-5 cm^-1 to 0.3×10-5 cm^-1.The curve of absorption coefficient is clearly broadened.The effect of the number of Mo vacancy defects on the absorption spectrum broadening is more obvious.With the increase of the number of vacancy defects in S atom,the reflectivity at the peak decreases gradually,and the decreasing trend of reflectivity slows down.When there are many vacancy defects in S atom,high reflectivity can be ensured in the long wavelength range.With the increase of the number of vacancy defects in Mo atom,the reflectivity tends to change linearly with the change of wavelength,and the reflectivity curve rises obviously,which can achieve a wide range of high reflectivity.