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Mode Modulation Based On Spoof Surface Plasmon Polariton Waveguide

Posted on:2019-11-03Degree:DoctorType:Dissertation
Country:ChinaCandidate:J J XuFull Text:PDF
GTID:1368330548980003Subject:Electromagnetic field and microwave technology
Abstract/Summary:PDF Full Text Request
Surface plasmon polariton(SPP)are two-dimensional electromagnetic(EM)fields,which are the result of coherent coupling of photons and free electron oscillations on the boundary of the metal and dielectric.These modes are characterized by high intensity and low dimensionality,particularly the advantages of subwavelength-scale confinements.The enhanced and localized fields can be harnessed to increase the sensitivity and performance of numerous physical phenomena and applications.SPP have attracted attracted the much attention because of their special optical properties.Owing to the advantages of confined EM fields in subwavelength scales,SPP have a lot of potential applications in enhanced transmission effect of subwavelength,data storeage,near-field optics,surface enhancement of Raman scattering,super-resolution imaging,and so on.As a natural and close relationship between photonic and plasmonic modes,SPP have great significance to study the excitation and transmission of the electromagnetic waves in sub-wavelength scales.Based on the ultrathin corrugated metal strips,the transmission and mode conversion mechanism of subwavelength spoof SPP waveguide structure is explored.By studying the transmission characteristics of subwavelength spoof SPP waveguide,we find a new coupling mechanism in the manipulation of mode conversion.The main contents are as follows:1.We propose a spoof SPP structure with diffraction radiation,which is achieved by introducing phase-reversal geometry into the SPP waveguide structure with ?-phase shift for adjacently reversed units.At the junction between two adjacent units,the discontinuity of the periodic structure can be viewed as a perturbation to generate space harmonics,thereby enabling efficient conversion of SPP modes into firee-space radiation modes.2.We propose a spoof SPP emitter which is composed of ultrathin corrugated metallic strips,exhibiting the directional radiation property.The spoof SPP emitter provides a way to quickly convert the SPP mode to a radiated mode.By controlling phase modulations produced by the phase-gradient metasurface on the ultrathin metallic strips,we demonstrate theoretically and experimentally that spoof SPP waves are converted into spatial propagating waves with high efficiency,which are further radiated with flexible beam steering.3.Two parallel ultrathin corrugated strips separated by a gap with mirror symmetry can be treated as a planar plasmonic cavity.Based on the coupled mode theory,SPP fields along a single waveguide in a certain frequency range can be readily coupled into two adjacent branch waveguides with the same propagation constants.We propose to load U-shaped particles anti-symmetrically at the ends of such two branch waveguides,showing a high integration degree of the feeding network.By controlling linear phase modulations produced by the U-shaped particle chain,we demonstrate theoretically and experimentally that the SPP fields based on bound modes can be efficiently radiated to far fields in broadside direction.The proposed method shows that the symmetry of electromagnetic field modes can be exploited to the SPP transmission network,providing potential solutions to compact power dividers and combiners for microwave and optical devices and systems.4.When a V-shaped unit is embedded in the plasmonic cavity,a strong perturbation is generated on the coupled SPP mode,resulting in a mode with anti-symmetric character over a wide frequency band.The mechanism of anti-symmetric mode excitation is based on?-phase difference between the currents on two strips.Due to the opposite-sign charges on the two strips,strongly localized fields are concentrated in the middle of the parallel metallic strips,and hence the anti-symmetric mode can be used to drive the radiated fields as SPP antenna.Experimental results show that a radiative mode is enhanced in the parallel corrugated metallic strips in a specific frequency region,resulting in SPP emissions.
Keywords/Search Tags:Spoof surface plasmon polariton, mode conversion, dispersion phase compensation, excitation of anti-symmetric modes
PDF Full Text Request
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