Complete Control of Smith-Purcell Radiation by Graphene Metasurfaces

Abstract

Smith-Purcell radiation results from charged particles that move closely to a periodic structure. In this work, we report the on-demand control of Smith-Purcell radiation by rationally designed graphene metasurfaces. Not only can we strongly enhance the efficiency of Smith-Purcell radiation, but also the amplitude, phase, and polarization state of the radiated wave can be fully manipulated by tuning the structure and Fermi level of the graphene metasurface. Through designing the geometric parameters of each unit cell of the metasurface, the intensity of the radiated wave from each unit cell can be changed from zero to maximum. Meanwhile, the phase of the radiated wave at any position of the metasurface can change within a range of 2π by adjusting the displacement of the patterned graphene structures. Utilizing these two properties, we demonstrate that we can steer the direction of the Smith-Purcell radiation and focus the radiated wave with dual focal points. Furthermore, a circularly polarized wave with an arbitrary phase can also be realized via introducing cross-polarization. Our findings provide a new way to design electron-beam-induced light sources as well as particle detectors with high efficiency and a compact footprint.

Tunable THz and Infrared Plasmonic Filters and Switches Based on Circular Graphene Resonator With 90$^\circ$ Bending of Output Port

“…The Fermi energy was varied from 0.1 eV to 1.1 eV and the corresponding frequency responses are plotted in Fig.3. It can be observed that the increase of the Fermi energy shifts the resonant frequency to higher values [21]- [23]. With change of F between 0.1 eV and 1.1 eV, the resonant frequency ranges from 5 THz to 15.96 THz for the dipole mode, from 7.2 THz to 22.56 THz for the quadrupole mode and from 8.2 THz to 25.9 THz for the hexapole one.…”

Controlling the degrees of freedom in metasurface designs for multi-functional optical devices

“…[162][163][164][165] For example, vanadium dioxide (VO 2 ), a thermal-sensitive phase change material, has been demonstrated successfully for beam scanning 166 or polarization switching. 167 On the other hand, applying electric elds is arguably the most direct and preferred method to realize dynamic control in liquid crystals, 168 graphene, 89,155,[169][170][171][172] and ITO. 173 Electrical reprogrammable holograms have been demonstrated in microwave frequencies by integrating electric diodes into the unit cells of metasurfaces.…”

Polariton Photonics Using Structured Metals and 2D Materials

“…that utilizes interband interaction), and the resonance is shifted to shorter wavelength when increasing the amplitude of Fermi energy. It should be noted that metasurfaces using patterned graphene structures have been proposed and demonstrated, aiming to manipulate and steer free‐space light in the THz and infrared regime …”

“…It should be noted that metasurfaces using patterned graphene structures have been proposed and demonstrated, aiming to manipulate and steer free-space light in the THz and infrared regime. [140][141][142][143] Although high modulation depth (≈90%) has been achieved, [98,133,136] the graphene modulators mentioned above cannot achieve low insertion loss and high modulation depth simultaneously. Another problem is that a large bias voltage, up to several tens or even one hundred volts, is needed to efficiently tune the Fermi energy of graphene.…”