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Photonic spin Hall effect (PSHE) of the transmitted wave presents promising applications in photonic spintronic devices, including inter-chip optical circuitry and quantum computing devices. These applications can benefit from phenomena such as the photon tunneling effect, frustrated total internal reflection, and the resonant optical tunneling effect. However, the mechanisms for enhancing PSHE of the transmitted wave are limited. In this study, an alternative strategy is proposed, which involves the utilization of topological edge states to enhance PSHE without relying on the aforementioned means. To demonstrate this effect, a heterostructure is designed, comprising two one-dimensional photonic crystals (PhCs) and a monolayer graphene. By leveraging the topological edge state, a significant enhancement of PSHE in the transmitted wave is observed, surpassing several times the incident wavelength. Furthermore, it is shown that the enhanced PSHE can be controlled and fine-tuned by adjusting the Fermi energy of monolayer graphene and the repetition numbers of the two PhCs. The enhanced and controlled PSHE in this heterostructure introduces possibilities for the development of novel optical components, such as switches, filters, modulators, and sensors. [ABSTRACT FROM AUTHOR]

Monolayer transition metal dichalcogenides have strong spin–orbit coupling and broken space inversion symmetry, which enable them to be the key building blocks in realizing spin and valley-related effects. Here, we report the spin and valley Hall conductivities of monolayer transition metal dichalcogenides in the presence of the magnetic proximity effect, which is introduced by a ferromagnetic substrate. It is found that the profile and magnitude of the spin and valley Hall conductivities in monolayer transition metal dichalcogenides are different with and without magnetic exchange interactions. This difference can be attributed to the asymmetrical band structure of monolayer transition metal dichalcogenides and chemical potential-dependent interband transitions. The former comes from the fact that the magnetic proximity effect can effectively break the time reversal symmetry and thus lead to the asymmetry of the band structures between K + and K − valleys, which causes the final changes in the spin and valley Hall conductivities. Our findings demonstrate that the magnetic proximity effect can affect the spin as well as valley Hall behaviors in monolayer transition metal dichalcogenides, and this strategy is applicable for other two-dimensional layered materials, which is promising for spintronic and valleytronic devices. [ABSTRACT FROM AUTHOR]

With the recent discovery of three dimensional Dirac semimetals, their integrations with the optoelectronic devices allow the novel optical effects and functionalities. Here, we theoretically report the photonic spin Hall effect in a periodic structure, where three dimensional Dirac semimetals and the dielectric materials are assembled into the stack. The incident angle and frequency dependent spin shift spectrum reveals that the spin shifts of the transmitted wave in this structure emerge the obvious peaks and valleys for the horizontal polarized wave and their magnitudes and positions display a distinct dependence on the incident angle around the specific frequency. These observations originate from its zero value of the effective perpendicular permittivity and its greatly reduced transmission in the multilayered structure, whose mechanism is different from those in the previous works. Moreover, both the peaks and valleys of the transmitted spin shift are significantly sensitive to the Fermi energy of three dimensional Dirac semimetals, whose magnitudes and positions can be tuned by varying it. Our results highlight the vital role of three dimensional Dirac semimetals in their applications of the spin photonic devices and pave the way to explore the tunable photonic spin Hall effect by engineering their Fermi energies. [ABSTRACT FROM AUTHOR]

BK7 glass has an unusual temperature-dependent refractive index and thickness, which provides a promising platform for uncovering the temperature-related optical phenomena and applications. Here, we theoretically demonstrate that monolayer graphene based BK7 glass grating structure has two Goosâ€"Hänchen (GH) peaks with respective magnitudes of 2564 λ and 1993 λ , and their corresponding reflectances are also high. The electromagnetic field distribution in this structure directly reveals that the enhanced GH shifts can be ascribed to the excitation of the guide mode resonances in the waveguide dielectric layer below BK7 glass grating structure and their high reflectances are granted by the constructive interferences between the reflected waves. In addition, the magnitudes of the GH peaks can be controlled by the temperature of BK7 glass as well as the chemical potential of monolayer graphene. We also evaluate the temperature sensing property of this structure based on the GH shifts and find that its maximum temperature sensitivity can be up to 5.0017 Ă— 10 4 ÎĽ m ° C âˆ' 1. The enhanced and controlled GH shift presented in monolayer graphene based BK7 glass grating structure shows promise for the applications, such as, optical sensors, temperature sensors, and optoelectronic detectors. [ABSTRACT FROM AUTHOR]

Monolayer MoS2 has excellent optical properties, but its low optical absorption hinders its application in optical absorbers. To improve its absorption performance, we design an aperiodic multilayer structure with monolayer MoS2, the dielectric materials Si and SiO2 arranged by Kolakoski sequence, and achieve the perfect absorption in the visible wavelength range because of its omnidirectional reflectivity. By optimizing the thicknesses of SiO2 (db), Si (dc) and the repetition number (N) of the unit cell, the absorption of the aperiodic multilayer structure can be greatly improved at normal incidence. When N is 3, this aperiodic multilayer structure achieves high absorption of up to 98% in the wavelength range from 350 to 450 nm. As N increases to 5 or 7, the average absorption of this aperiodic multilayer structure exceeds 90% in the 350–600 nm wavelength range. In addition, we verify that the broadband and high absorption obtained in this aperiodic multilayer structure is robust against the angle of incidence and polarization of the incident wave. Our results suggest an alternative configuration with monolayer MoS2 to realize the broadband and perfect absorption, which is useful for future applications in solar cell or photodetectors. [ABSTRACT FROM AUTHOR]