We present a non-intuitive but still practically implementable silicon meta-atom with strong electrical tunability. We used topological optimization on a 20×20-variable silicon-on-insulator grid and achieved tunability by using JRD1, a stable electrooptic polymer. The electric potential is applied on two ITO electrodes, and a peak shift of 0.6 nm V−1 is achieved in the optical communication E and S bands. The proposed device can be regarded as a demultiplexer or channel selector on a coarse wavelength-division-multiplexing system, with an extinction ratio between adjacent channels of ∼14 dB.
We report the integration of an open-source software-defined radio (SDR) receiver to detect and track in realtime harmonic radar echoes produced by a non-linear device (transponder) mounted on a very small target. We describe a series of experimental measurements that were conducted to validate the sensitivity of the receiver system. In addition, we describe the implementation of a high-speed digital signal processing and a target detection algorithm. Finally, the experimental data and the results after the signal processing for detection are presented. In particular, it is demonstrated that the platform is a cost-effective receiver solution for the detection of transponders in Harmonic radar applications, relatively simple to program and implement.
Grating-coupled excitation of surface plasmon-polariton waves guided by the interface of a metal and an anisotropic dielectric material evinces morphological effects arising from the divergence of structural anisotropy (grating) from constitutive anisotropy (dielectric material). Even if the metal is replaced by an isotropic dielectric ma- terial, the same effects are seen in the excitation of Dyakonov surface waves. The morphological effects vanish with constitutive anisotropy, as exemplified with a columnar thin film (CTF) as the dielectric material. Both p-polarized and s-polarized incident plane waves can excite the surface plasmon-polariton (SPP) waves as well as Dyakonov surface waves, provided that either the plane of incidence and/or the morphologically significant plane of the CTF do not coincide with the grating plane.
Excitation of Dyakonov surface waves guided by a plane wave incident on a columnar thin film (CTF) deposited on a surface-relief grating decorating a dielectric substrate was studied using the rigorous coupled-wave approach, when the grating plane, the plane of incidence, and the morphologically significant plane of the CTF are all different. The absorptance for a specific linear polarization state of the incident plane wave was plotted as a function of the polar angle of incidence, at a fixed azimuthal angle, and those absorptance peaks were identified that are independent of the thicknesses of the CTF and the dielectric substrate. The angular locations of these absorptance peaks were correlated with the solution of the canonical boundary-value problem for surface-wave propagation. Dyakonov surface waves can be excited in a wider range of directions in the interface plane by p-polarized illumination than by s-polarized illumination. When the incidence and the grating planes do not coincide, it is possible to excite Dyakonov surfaces for multiple values of the polar angle of incidence.
The excitation of surface-plasmon-polariton (SPP) waves guided by a columnar thin film (CTF) deposited on a one-dimensional metallic surface-relief grating was studied employing the rigorous coupled-wave approach, when the grating plane, the plane of incidence, and the morphologically significant plane of the CTF are all different. The incident plane wave in this grating-coupled configuration could be either p- or s-polarized. The absorptance was plotted against the polar angle of incidence at a fixed value of the free-space wavelength, and absorptance peaks were correlated with the solution of the dispersion equation of the underlying canonical boundary-value problem for SPP waves. Both p-polarized and s-polarized plane waves can excite SPP waves, provided that either the plane of incidence and/or the morphologically significant plane of the CTF do not coincide with the grating plane. None, one, or multiple SPP-wave excitations are possible, depending on the orientations of the grating plane and the morphologically significant plane with respect to the plane of incidence. The direction of propagation of an SPP wave thus excited may not wholly lie in the plane of incidence.
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