No abstract

High quality factor and small modal volume for compact, integrable optical devices have always been of great demand. Although metamaterials may be designed to achieve selected mode confinement at a subwavelength scale, structures themselves have retained a large size. We address the issue of the subwavelength mode confinement in structures of reduced size by utilizing unique properties of spoof surface plasmon polaritons (SSPP). While SSPP modes are commonly considered in the context of periodic structures, we demonstrate that the SSPP formation does not depend crucially on periodicity and, therefore, meta-structures of minimal length can support well-formed spoof plasmon state. This general property is explicated through our study of the transmission spectrum of a three-cell waveguide with the spoof plasma frequency of the middle cell (defect cell) different from that of remaining cells (host). The SSPP state in the defect cell supports resonant tunneling manifested by a narrow transmission resonance inside the bandgap of the host structure. Despite the minimal length of the structure, the localized defect SSPP mode is characterized by very high quality (∼ 10 5 ) and Purcell (∼ 10 3 ) factors. The proposed concept can be a promising alternative for making a miniaturized sources, information storage and sensing devices at low terahertz frequencies.

States of the electromagnetic field confined near a periodically corrugated surface of a perfect conductor, spoof surface plasmon polaritons (SSPP), are approached systematically based on the developed adaptation of the mode matching technique to the transfer matrix formalism. Within this approach, in the approximation of narrow grooves, systems with arbitrary transversal structure can be investigated straightforwardly, thus lifting the restrictions of the effective medium description and usual implementations of mode matching. A compact expression for the SSPP coupling parameter accounting for the effect of higher Bloch modes is found. The results of the general analysis are applied for studying the effect of dielectric environment on SSPP spectra. It is shown that the effective SSPP plasma frequency is unaffected by the dielectric constant of the medium outside of the grooves and the main effect of sufficiently wide dielectric slabs covering the corrugated surface is described by simple rescaling of the maximal value of the Bloch wavenumber and the coupling parameter. Additionally, in the case of a thin dielectric layer, it is shown that SSPP are sensitive to variation of the thickness of the layer on the sub-wavelength scale.

Spoof surface plasmon polariton (SSPP) is an exotic electromagnetic state that confines light at a subwavelength scale at a design-specific frequency. It has been known for a while that spoof plasmon mode can exist in planar, thin structures with dispersion properties similar to that of its wide threedimensional structure counterpart. We, however, have shown that spoof plasmons in thin structures possess some unique properties that remain unexplored. Our analysis reveals that the field interior to SSPP waveguide can achieve an exceptional hyperbolic spatial dependence, which can explain why spoof plasma resonance incurs red-shift with the reduction of the waveguide thickness, whereas common wisdom suggests frequency blue-shift of a resonant structure with its size reduction. In addition, we show that strong confinement can be achieved over a wide band in thin spoof plasmon structure, ranging from the spoof plasma frequency up to a lower frequency considerably away from the resonant point. The nature of lateral confinement in thin SSPP structures may enable interesting applications involving fast modulation rate due to enhanced sensitivity of optical modes without compromising modal confinement.

Signal-modulation of a spoof surface plasmon polarition interconnect is attained by controlling the channel conductance of a transistor incorporated in the metallic grove. Amplitude modulation of SSPP signal has been analytically derived and numerically verified.