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Research Of The Properties Of Two-dimensional Subwavelength Defective MIM Waveguides

Posted on:2014-02-27Degree:DoctorType:Dissertation
Country:ChinaCandidate:L WangFull Text:PDF
GTID:1220330401973932Subject:Physics
Abstract/Summary:PDF Full Text Request
Surface plasmon polaritons (SPPs), also known as surface plasmon, is a surfacewave formed by the interaction between free eletrons and external photons, which isstrongly bounded to the metal and dielectric interface. The plasmonics waveguideshave aroused extensive attentions in recent years due to the strong local andconduction characteristics at subwavelength scale. Compared with the metal-insulatorand insulator-metal-insulator (IMI) waveguides, the metal-insulator-metal (MIM)waveguid have many special performances, such as smaller mode size, strongerconfinement of light and shorter propagation length. Based on this, in this thesis, westudied the electromagnetic transmission properties of the MIM plasm onicswaveguides in the visible to near-infrared spectral region. We designed and exploredseveral plasmonics MIM waveguide structures, and realized the control of theelectromagnetic waves at micro and nano scale.The main research works and conclusions are as follows:The MIM plasmonics waveguide which is modified by a vertical slit is proposedand the transmission characteristics are numerically investigated in the visible tonear-infrared spectral region. We mainly studied the influence of the transmis sioncharacteristic for the size of the vertical slit for single frequency electromagneticwave. The results show that the vertical slit in the waveguide structure is similar to aFabry-Pérot resonant cavity. In the slit, the wave will reflect at the end of the slit andinterference each other with the incident wave. When the size of the slit satisfies theFabry-Pérot resonance, the waves will form a standing wave and the electromagneticenergy can be localized in the vertical slit. When the geometric of the slit is tuned, itis found that the length of the slit has a period for entirely localize the singlefrequence wave.A MIM waveguide with multiple-teeth-shaped graded depths is numerically andtheoretically demonstrated. Analysesed the effect of the effective refractive index bythe width of the waveguide, the wavelength of the incident light and so on. Thetransmission characteristics of the proposed structure are expounded reasonably bythe scattering matrix theory. It is found that the multiple-teeth-shaped graded depthsMIM waveguide can strongly slow light as the propagation velocities of SPPs arereduced over a large frequency bandwidth at visible wavelengths domain. Since the wavelength of the trough of transmission is dependent on the depth of thetooth-shaped dielectric in the MIM waveguide, the guided SPPs at differentfrequencies can be localized at different spatial positions of the multiple-teeth-shapedgraded depths MIM waveguide. Moreover, the separation between trapped waves canbe tuned by changing the grade of the tooth-shaped depths and the lifetime of SPPs inthe waveguide may be long enough for some meaningful nano-photonic applications.A compact plasmonic branch-shaped MIM waveguide with a triangular-annularchannel is proposed and the transmission characteristics are investigated. We mainlyfocus on the transmission symmetry of the structure influence on the propagationnperformance. It shows that all-band waves can transmit through the structure when ithas transmission symmetry. As the output position of the waveguide is dislocated, i.e.the transmission symmetry is broken, a typical filtering function is obtained and thetransmissivity of the resonance frequency depends on the destroyed degree ofsymmetry. The controllable transmissivity phenomenon can be interpreted by thephase difference between the two branched SPPs propagating along thetriangular-annular channel at the output of the structure. Moreover, the filteringwavelength can be selected by changing the length of the triangular-annular channelwhich is similar to a ring resonator.We propose a two-dimensional plasmonics MIM waveguide structure withmultiple-ring shaped. The local effect and wavelength demultiplexing function areinvestigated. It is found that the multiple-ring shaped MIM waveguide can realize the―ra nbown effect‖, i.e. the incident waves can be trapped in the subwavelength ringwith different wavelength in different rings. The wavelength of the trapped waves isdependent on the resonant wavelength of the ring which is related to the geometry andthe effective refractive index of the subwavelength ring. Based on the s kin penetrationeffect, the trapped energy can be exported by the output waveguides which are addednearby the rings, respectively. The waves can be divided by control the geometricalparameters of the subwavelength rings.
Keywords/Search Tags:Surface plasmon polaritons (SPPs), Subwavelength metallic structures, Metal-Insulator-Metal (MIM) waveguide, Plasmonic filters
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