Nonlinear Phenomena in Photonic Nanostructures

: Modulational Instabilities And Solitons

Abstract

This thesis discusses nonlinear effects, such as modulation instability and solitons innano-structured waveguides. The nanoscale optical waveguides have extremely smalltransverse dimensions, which can provide tight confinement of light. Therefore, bychanging the waveguide geometry, the waveguide dispersion can be strongly altered. Onthe other hand, the confinement also enhances the nonlinear dispersion, allowing fornonlinear optical phenomena supported by dispersion of nonlinearity.The new models governing evolution of the amplitudes of components of the opticalwaves interacting in the waveguides are derived for continuous wave and pulse waveusing perturbation expansion method. The new modulation instability condition is found,as we take into account the dispersion of nonlinearity which is enhanced through a strongvariation of the modal profile with the wavelength of light in sub-wavelength waveguides.We demonstrate that this dispersion of nonlinearity can lead to the modulation instabilityin the regime of normal group velocity dispersion through the mechanism independentfrom higher order dispersions of linear waves for continuous wave. We address that thenew mechanism highly associated with dispersion of nonlinearity in sub-wavelengthsemiconductor waveguide induces the modulation instability in picsecond regime togetherwith the cascaded generation of higher-order sidebands. The impact of the dispersion ofnonlinearity on spectral broadening of short pulses in a silicon waveguide also isconsidered.We study the temporal evolutions of fundamental and one-ring solitary waves with phasedislocation in dielectric-metal-dielectric waveguides with PT-symmetry and numericallyanalyze the properties of these nonlinear localized modes and, In particular, revealdifferent scenarios of their instability.

Date of Award	23 Apr 2014
Original language	English
Awarding Institution	University of Bath
Supervisor	Dmitry Skryabin (Supervisor)