Ph.D Thesis

Ph.D StudentFeigenbaum Eyal
SubjectSlow Wave Phenomena in Plasmonic Nano-Circuitry
DepartmentDepartment of Electrical and Computer Engineering
Supervisor PROF. Meir Orenstein
Full Thesis textFull thesis text - English Version


Surface Plasmon Polariton (SPP) is a surface wave propagating on the interface between metal and a dielectric. The plasmonic waves are promising candidates for realizations of optical nano-circuitry, as an alternative to the ordinary photonics devices - the latter are limited to dimensions larger than half-wavelength. My study explores the extreme boundaries we may achieve from plasmonic waves by manipulating the plasmonic device structure.

Starting with 1D configurations - we examined the power flow dynamics of plasmonic waves is examined, shedding light on the unique bi-directional power flow and its relations to the "slow light" and "backward wave" characteristics of plasmonics. The subwavelength size of the plasmonic mode is the core mechanism to the unique excessive side-coupling, when two plasmonics waveguides supporting “slow wave” are crossing, exhibiting a substantial intercoupling as an incoming pulse is perfectly split into 4-arms.

2D plasmonics waveguides can be uniquely realized by guiding plasmonic waves on a metal wedge. By tailoring an analysis method for this configuration, we predict the existence of plasmonic modes having modal size substantially smaller than the wavelength, exhibiting spectral regions of very slow light as well as backward propagating waves.

Plasmonic structures in 3D are important for the realization of plasmonic nano-resonators. Within a dielectical gap between two metal plates, the slow wave nature of the plasmonic polariton gap mode allows the indefinite reduction in the inter-metal interfaces distance, as well as in the in-plane (transverse) dimensions, prevailing the conventional "diffraction limit" associated with light waves. Therefore, nano-circuitry could be implemented by introducing reduced size 2D photonic components into this reduced diffraction 'sub-space'. We have demonstrated an ultrasmall modal volume resonator (modal volume of ~(36nm)3 at free space wavelength of ~700nm) with moderate Quality-factor (Q~170). The confinement was further enhanced to modal volume of 0.0002l3, by adding another effect, namely negative reflection phase mirrors. This nano-particle plasmon exhibits Q-factors significantly larger than the quasi-static prediction for structures which are substantially smaller than the wavelength, elucidating that retardation effects can play a significant role for metal nano-structures facilitating plasmons.

We study the plasmonic effect on nonlinear guided beams diffraction, namely the confinement enhancement of plasmon-soliton beams. The analysis includes the formulation of the nonlinear wave equation for TM polarization, from which a plasmon-soliton hybrid beam emerges having possible nano-dimensions.