Abstract- Tunable graphene plasmonic Y-branch switch in the terahertz region using hexagonal boron nitride with electric and magnetic biasing

Ali Farmani, Mahdi Yavarian, Abbas Alighanbari, Mehdi Miri, and Mohammad H. Sheikhi

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-56-32-8931

A tunable graphene plasmonic Y-branch switch at THz wavelengths is proposed. The effects of magnetic and electric biasing are studied to harness the transmission of the transverse electric and magnetic guided mode resonances. In the structure, hexagonal boron nitride is utilized as a substrate for graphene. The application of hexagonal boron nitride, with the advantages of high mobility and ultralow ohmic loss, introduces a promising alternative substrate for graphene. Analytical and numerical results show that, by slight variation of the doping level in graphene through magnetic and electric biasing, the characteristics of the propagation of the guided mode resonances can be manipulated. A large extinction ratio of 40 dB at a wavelength of 60 μm is obtained. Besides, the proposed switch shows a low insertion loss of about 1 dB and a relatively large optical bandwidth of 1 μm. The electric biasing is of the order of 0.1 mV. Additionally, with the presence of magnetic biasing, a compact switch with a size of 25 μm is achieved. Showing a high extinction ratio, low insertion loss, and compact size, the proposed switch can find potential applications in graphene plasmonics integrated devices.

© 2017 Optical Society of America

Abstract-Tunable graphene plasmonic Y-branch switch in the terahertz region using hexagonal boron nitride with electric and magnetic biasing

Ali Farmani, Mahdi Yavarian, Abbas Alighanbari, Mehdi Miri, and Mohammad H. Sheikhi

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-56-32-8931

A tunable graphene plasmonic Y-branch switch at THz wavelengths is proposed. The effects of magnetic and electric biasing are studied to harness the transmission of the transverse electric and magnetic guided mode resonances. In the structure, hexagonal boron nitride is utilized as a substrate for graphene. The application of hexagonal boron nitride, with the advantages of high mobility and ultralow ohmic loss, introduces a promising alternative substrate for graphene. Analytical and numerical results show that, by slight variation of the doping level in graphene through magnetic and electric biasing, the characteristics of the propagation of the guided mode resonances can be manipulated. A large extinction ratio of 40 dB at a wavelength of 60 μm is obtained. Besides, the proposed switch shows a low insertion loss of about 1 dB and a relatively large optical bandwidth of 1 μm. The electric biasing is of the order of 0.1 mV. Additionally, with the presence of magnetic biasing, a compact switch with a size of 25 μm is achieved. Showing a high extinction ratio, low insertion loss, and compact size, the proposed switch can find potential applications in graphene plasmonics integrated devices.

© 2017 Optical Society of America

Abstract-Tunable resonant Goos–Hänchen and Imbert–Fedorov shifts in total reflection of terahertz beams from graphene plasmonic metasurfaces

Ali Farmani, Mehdi Miri, and Mohammad H. Sheikhi

https://www.osapublishing.org/josab/abstract.cfm?uri=josab-34-6-1097&origin=search

Highly tunable enhanced lateral displacements in the center of gravity of a totally reflected light beam from a graphene plasmonic metasurface are investigated. Multiple reflections of the incident beam, and the resonance coupling between the incident beam and the surface modes of the graphene metasurface in each reflection, are employed to enhance the Goos–Hänchen and Imbert–Fedorov shifts in the proposed structure. It is shown that spatial Goos–Hänchen and Imbert–Fedorov shifts as high as 1089𝜆0$1089{\lambda }_0$ and −44.66𝜆0$-44.66{\lambda }_0$ (𝜆0${\lambda }_0$: incident wavelength) are achievable in the proposed structure. The effects of different parameters, including the incident beam waist, temperature, the scattering time, and the chemical potential of the graphene, on the shift values are then studied. Because of the strong light confinement in the surface modes of the graphene metasurface, the dispersion properties of these modes, and, therefore, the coupling strength between the incident beam and these modes, are highly sensitive to the parameters of the reflecting structure and the incident beam itself. The high sensitivity of the coupling strength between the incident beam and the surface modes is then exploited to tune the shift values. It is shown that by introducing a small change of Δ𝜇𝐶=0.02  eV$\mathrm{\Delta }{\mu }_C=0.02\mathrm{eV}$ in the chemical potential of the graphene, the spatial Goos–Hänchen and Imbert–Fedorov shift variations of 855𝜆0$855{\lambda }_0$ and −31𝜆0$-31{\lambda }_0$ can be achieved, respectively. The wide range of lateral shift variations along with the relatively small required actuation power support the application of the proposed structure in the realization of optical devices, such as temperature sensors and switches.

© 2017 Optical Society of America