Tera Hertz Plasmonic Devices for Photonic Integrated Circuit

Abstract

newline i newlineAbstract newlineThe last decade has seen the new frontiers being laid down in field of Plasmonics which initiated in the history with a perspective of providing confinement and localization at the nanoscale which caters variety of applications. This emerging field which takes into account the benefits of nanometer-scale electronics and ultra-fast photonics leads into providing next generation on chip nanoscale devices which adhere to some of the unique possibilities like higher bandwidth, less power consumption, portability, high speed computation etc. gained by the light/matter interaction. Plasmonics exhibits some of the promising applications in solar energy, pharmacology and nanocircuitry etc. newlineThe present advancements which are dealing with the development of novel materials for the integrated photonic devices witness the use of plasmonic devices as one of the promising candidates to overcome the limitations of diffraction limit faced in the photonic systems. In particular the electromagnetic waves which are propagating in the nanophotonic devices makes the use of Surface Plasmon Polaritons (SPPs). Such waves being propagated in the metal-dielectric interface are led by the metallic nanogeometries and structures which work well beyond the diffraction limit and manipulates the light into the subwavelength spots. The plasmon guiding used to couple the light is achieved through waveguide coupling, metallic gratings, prism coupling etc. Plasmonic materials like transparent conducting oxides and transition metal nitirides offers an advantage to be integrated with the existing nanophotonic and nanoelectronic devices to generate composite devices to bring together new levels of technological opportunities. newlineThe light manipulation by the photonic and plasmonic devices includes both active and passive components utilizing the waveguides and modulators. This dissertation emphasizes on the simulation of design of plasmonic modulators using different geometries and materials which are used as a filter, switch and resonator respectively. Plasmonic modulators are useful for transforming the electrical signals into the surface plasmon polaritons (SPPs) for their propagation in metal nanostructures and vice versa. They have been developed as new generation low power and high-speed optoelectronic newlineii newlinedevices which provides a great choice and an alternative to the conventional devices. The plasmonic modulators proposed in the thesis make the use metal-dielectric-metal waveguides and the external electric signals are used to control or limit propagation via the dielectric medium used in this. The research work includes an Ultra-Compact Optical Modulator using Indium Tin Oxide Material and Metal- Dielectric-Metal Waveguide Structure. This design is beneficial in providing good tuning and modulation by using Indium-Tin-Oxide, second design includes an Ultra-compact Plasmonic Modulator using Elasto-optic Effect and Resonance Phenomena, using elasto-optic effect it provides fine extinction ratio of modulation and admissible losses. Third design is of ultra-compact optical switch using Phase transition phenomenon in VO2 , this one acts a plasmonic switch which exploits VO2 filled Metal-Dielectric-Meatal waveguide whose functioning informs about the on and off states corresponding to the DC voltage. Also, there is a Compact Optical Switch Using Phase Transition Phenomenon Of Tin, wherein the Titanium Nitride is beneficial over Vanadium Oxide for being cheaper and MDM based plasmonic switch has been designed as the novel approach. All these modulators and switches extend a variety of applications towards its non-linear characteristics, helpful in the nanodesign fabrication. newlineFurther the theoretical designs are relative to the simulation results obtained through Finite element method. All the designs are analyzed using COMSOL FEM simulation software. The main emphasis of the thesis is designing of various plasmonic modulators with ultra-compact waveguides in the form of MDM and using an active core of dielectric material like ITO, VO2 etc. The refractive index of these materials change with respect to the electric field applied and the gap introduced in the MDM waveguide offer the resonance spectrum respectively along with the fact that such rectangular groves in the waveguide structure are responsible for the formation of stop bands and act as a band stop filter for certain applications where ultra-compact modulators are beneficial owing to their advantages. Different structure regimes have been discussed by using detailed simulation and their working characteristics are identified which form the research study of the Plasmonic modulators.