| Two-dimensional materials,such as monolayer graphene and monolayer Mo S2,have the characteristics of ultra-thin thicknesses,good flexibilities and high mobilities,which make them attracted extensive attention in the field of interaction between light and matter.Periodic nanostructures exhibit significant modulation of electromagnetic waves propagation.For example,the periodicity of grating structure can regulate the incident beam by means of scattering,reflection or transmission.And the periodic change of the dielectric constant with space in photonic crystals can also be used to control the propagation of electromagnetic waves.These characteristics have been widely used in optical communication and optical detection.In recent years,the combination of two-dimensional materials and periodic nanostructures has made great breakthroughs in improving optical properties,such as the enhancement of optical absorption rate,magneto-optical effect and Goos-H（?）nchen shift.The Goos-H（?）nchen shift refers to the lateral shift of the actual reflected beam relative to the predicted position of geometric optics when the light is incident on the interface between two media.This effect has significant potential for applications such as high-performance sensitive sensors and photoelectric detection.In this paper,the Goos-H（?）nchen shift of several composite structures containing monolayer Mo S2 are investigated by using rigorous coupled wave analysis,the transmission matrix method and the stationary phase approach.The main research works of this paper are listed as follows:First,a symmetric or asymmetric dielectric grating structure with monolayer Mo S2 is proposed and the Goos-H（?）nchen shift of the reflected beam in this structure is investigated by combining the rigorous coupled-wave analysis method and the stationary phase approach.The results show that the combination of monolayer Mo S2 and the above two types of dielectric gratings can achieve the enhancement of the Goos-H（?）nchen shift.In particular,the asymmetric grating structure with monolayer Mo S2 has achieved the Goos-H（?）nchen shift as high as 9490 times the incident wavelength,which is about 3.5 times as large as that in the symmetric dielectric grating structure with monolayer Mo S2 at the same working wavelength.This enhanced Goos-H（?）nchen shift can be attributed to the excitation of the guided mode resonance in the dielectric grating structure.In addition,the magnitude and sign of the Goos-H（?）nchen shift in this structure are highly sensitive to the geometrical parameters of the asymmetric dielectric grating structure.This work provides a reliable way to improve the Goos-H（?）nchen shift of transition metal dichalogenides,which is expected to be widely used in high-precision sensors and optical switches.Secondly,a multilayer structure containing monolayer Mo S2,metal layer and the one-dimensional photonic crystal is designed and the Goos-H（?）nchen shift of the reflected beam in this structure is investigated by the transmission matrix method and the stationary phase approach.The results show that the Goos-H（?）nchen shift in the multilayer structure is 3458.3 times of the incident wavelength than for the structure without monolayer Mo S2,which is about 97.8 times as large as the former.The enhanced Goos-H（?）nchen shift in the multilayer structure originates from the coupling between the surface plasmon polaritons in the surface of the metal layer and the dielectric layer and the waveguide modes inside the photonic crystal,which greatly enhances the interaction between the incident light and the multilayer structure.This result provides a new design perspective for enhancing the Goos-H（?）nchen shift of monolayer Mo S2,which will greatly facilitate their applications in the fields such as filters and photodetectors.Finally,a one-dimensional defective photonic crystal structure with monolayer Mo S2 and monolayer graphene is designed and the Goos-H（?）nchen shift of the reflected beam in this structure is investigated by the transmission matrix method and the stationary phase approach.It is found that the structure can achieve a significant Goos-H（?）nchen shift with an amplitude up to-9226.3 times of the incident wavelength at the specified operating wavelength.This enhanced Goos-H（?）nchen shift can be understood from the generation of the localized defect modes in the defective photonic crystal structure enhancing the interaction between the incident light and the structure.In addition,this structure has a tunable Goos-H（?）nchen shift by varying the geometrical parameters of the dielectric material and the chemical potential of monolayer graphene.The concept of coexistence of monolayer Mo S2 and monolayer graphene in defective photonic crystal allow the tunability of the Goos-H（?）nchen shift of monolayer transition metal dichalogenide proposed in this paper,which indicates its promising potential for the design of various optoelectronic devices. |
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