INTEGRATED PLASMONIC WAVEGUIDES AND DEVICES

Abstract

In this thesis metal nanoparticles of different shapes and sizes have been used to manipulate the properties of different plasmonic devices with enhanced transmission and high performance. Array of metal nanoparticles embedded in dielectrics exhibit plasmonic band gap that allows plasmon propagation with larger propagation length and low losses. We consider silver metal nanorods embedded on silicon on insulator (SOI) substrate for devising ultra-compact plasmonic waveguides like straight waveguide, y-splitter and bend design. Proposed waveguide exhibit low loss propagation, larger propagation length and strong confinement of the traversing plasmonic mode. These components can be used for high density plasmonic circuitry. Low loss performance of such waveguides is further used to design highly sensitive plasmonic sensor used in sorting and classification of cancer cells. Plasmonic Mach-Zehnder interferometer (PMZI) is proposed for refractive index sensing assessed in terms of wavelength and phase shift. Proposed PMZI comprises of array of silver nanorods embedded upright into silicon on insulator thus exhibiting surface plasmon polariton band gap (SPPBG) effect. This arrayed system triggers local field enhancement promoting sensing proficiency of the device. As, metal nanoparticles exhibit very high local field therefore, ellipsoidal plasmonic crystal is proposed which flaunts Fano resonance with applications in switching and lasing. The geometry of metal nanoparticles controls the plasmon resonance. Scattering models for ellipsoidal and cylindrical nano particles are compared and it is found that the spectral interference between the cavity mode and the background scattering mode results in sharp asymmetric peak, which is the defining characteristic of Fano resonance. Enhancement in the asymmetric vi line shape of Fano resonance is observed and extensively examined for cavities in plasmonic crystals of ellipsoidal silver nanoparticles with hexagonal arrangement. When the size of metal nanoparticles is less than 10nm and interparticle distance is in sub-nanometer dimensions, the system exhibit astounding behaviour. Skin depth dependence of metal nanoparticles system showing resonant plasmon tunnelling is studied. Gradient potential dependent skin-depth theory (GPST) is introduced to study resonant plasmon tunnelling in silver nanodisk dimer system. The region between adjacent silver nanodisks at subnanometer spacing, exhibit gradient potential due to the property of its geometry leading to the formation of tunnelling zone and is substantiated by finite difference time domain (FDTD) computational method. The proposed GPST can be used to predict the performance of plasmon tunnel diode, plasmon tunnelled field-effect transistors, plasmonic Josephson junction assisted superconductivity etc. Further, incorporating metal nanoparticles with semiconductors give rise to plasmon-exciton coupling and hence have been used in plexcitonic interaction for devising composites. Plexcitonic systems formed by multi-layered silvergallium arsenide-silver (Ag-GaAs-Ag) quantum nano-lenses are proposed and various optical properties are studied. Cavity defect support strongly confined mode. As the cavity mode resonates in ultra-violet regime, it can be an alternative for excimer lasers. Plasmonics offer ultrafast, ultra-small and highly efficient devices. With metal nanoparticles tailoring and manipulation of light has become interesting thus the technology offers excellent applications with desired properties. Nano scale planar waveguides, faster chip and important role in cancer therapy are just a few examples of the unique applications it acclaims.