Temperature tunability of surface plasmon enhanced Smith-Purcell terahertz radiation for semiconductor-based grating

Thermally tunable Dyakonov surface waves in semiconductor nanowire metamaterials

The development of engineered metamaterials has enabled the fabrication of tunable photonic devices capable of manipulating the characteristics of electromagnetic surface waves. Integration of semiconductors in metamaterials is a proven approach for creating thermally tunable metamaterials through temperature control of the semiconductor carrier density. In this paper, an interface consisting of an isotropic dielectric material as a cover and an indium antimonide (InSb) nanowire metamaterial as a substrate, is theoretically introduced to investigate the propagation conditions of Dyakonov surface waves in terahertz (THz) frequencies. Various temperature-dependent properties of Dyakonov surface waves in such a geometry is studied, including allowed THz regions, angular existence domain, dispersion relation, directionality, localization degree and figure of merit. The proposed configuration due to the presence of significant birefringence in InSb nanowire metamaterial, has potential applications in THz sensing, imaging and spectroscopy.

THz Smith-Purcell and grating transition radiation from metasurface: experiment and theory

We report the results of experimental and theoretical studies of monochromatic coherent terahertz radiation generated by a short relativistic electron bunch interacting with a metasurface. The metasurface consists of subwavelength metal elements arranged on a dielectric substrate. The constructed theory explains the experimental spectra of Smith-Purcell radiation and grating transition radiation with very high precision. The orientational distribution of transition radiation shows a fine structure, which, as we suppose, may be due to contribution of coupling between the metasurface's elements.

Surface plasmons manipulated Smith-Purcell radiation on Yagi-Uda nanoantenna arrays

An electron bunch (e-bunch) passing through an insulator-metal-insulator (IMI) substrate can excite surface plasmons (SPs) on the substrate. Recent studies demonstrate that Smith-Purcell radiation (SPR) from one-dimensional gratings on an IMI substrate can be manipulated and enhanced by e-bunch excited SPs. However, under this configuration, only the emission along the direction of electron moving can be controlled. To steer both the azimuthal and polar angles of the far-field emission pattern requires other mechanisms. In this work, the SP-manipulated SPR with a Yagi-Uda nanoantenna (YUNA) array on an IMI substrate for generation of light beams with designed far-field patterns is proposed and explored by computer simulations. Emission of SPR along and perpendicular to the direction of electron movement can be manipulated by designing grating period and YUNA structure, respectively. Dependence of the azimuthal and polar angles of emitted light beam on geometry parameters of feed and directors of YUNA are elucidated. Furthermore, emission of multiple beams containing a single wavelength and multiple wavelengths with required far-field angles can be achieved using different groups of YUNA arrays on different IMI substrates. The proposed mechanism may have applications for light sources, optical imaging, optical beam steering, holography, microdisplay and cryptography.