Self-Induced Transparency Solitons in Nanophotonic Waveguides
Author(s)
Pusch, Andreas
Type
Thesis
Abstract
This thesis explores the existence and properties of self-induced transparency (SIT)
solitons in nanophotonic waveguides. SIT solitons are shape-preserving solutions of
the semi-classical Maxwell-Bloch equations, a system of nonlinearly coupled differential
equations. In a first investigation, collisions of counterpropagating simultons (SIT
solitons in absorbing three-level systems) are studied numerically in the plane-wave approximation
and a polarisation- and group-velocity dependent soliton birth is uncovered.
Apart from their fundamental interest, such light-light interaction effects may be of use
for optical computing applications if they can be transferred to tightly confined light
pulses. Confining light is usually achieved by using dielectric waveguides that exhibit
group velocity dispersion leading to chirped pulses, which experience absorption when
entering an absorbing medium. If the chirp is strong enough and the pulse intense
enough, they can even completely invert an absorber. When investigating chirped pulse
propagation through a dense ensemble of two-level system it is found that the chirped
pulses dynamically reshape into unchirped pulses experiencing transparency. Furthermore,
the conditions on the waveguide geometry to enable SIT are analysed, identifying
a nanophotonic slot waveguide with a low-index gap, exhibiting high electric field enhancement
and a homogeneous field profile, as the ideal candidate system for guided SIT
solitons. This analysis is supported by two-dimensional numerical calculations that show
the solitary character is maintained during propagation if the absorber density is high
enough to ensure a slow-down of the pulse and to thus counteract the waveguide dispersion.
Finally, the soliton birth due to simulton collisions and optical memory schemes
proposed for plane-wave SIT are investigated in the two-dimensional slot waveguide and
found to also be possible in this geometry.
solitons in nanophotonic waveguides. SIT solitons are shape-preserving solutions of
the semi-classical Maxwell-Bloch equations, a system of nonlinearly coupled differential
equations. In a first investigation, collisions of counterpropagating simultons (SIT
solitons in absorbing three-level systems) are studied numerically in the plane-wave approximation
and a polarisation- and group-velocity dependent soliton birth is uncovered.
Apart from their fundamental interest, such light-light interaction effects may be of use
for optical computing applications if they can be transferred to tightly confined light
pulses. Confining light is usually achieved by using dielectric waveguides that exhibit
group velocity dispersion leading to chirped pulses, which experience absorption when
entering an absorbing medium. If the chirp is strong enough and the pulse intense
enough, they can even completely invert an absorber. When investigating chirped pulse
propagation through a dense ensemble of two-level system it is found that the chirped
pulses dynamically reshape into unchirped pulses experiencing transparency. Furthermore,
the conditions on the waveguide geometry to enable SIT are analysed, identifying
a nanophotonic slot waveguide with a low-index gap, exhibiting high electric field enhancement
and a homogeneous field profile, as the ideal candidate system for guided SIT
solitons. This analysis is supported by two-dimensional numerical calculations that show
the solitary character is maintained during propagation if the absorber density is high
enough to ensure a slow-down of the pulse and to thus counteract the waveguide dispersion.
Finally, the soliton birth due to simulton collisions and optical memory schemes
proposed for plane-wave SIT are investigated in the two-dimensional slot waveguide and
found to also be possible in this geometry.
Date Issued
2012
Date Awarded
2012-11
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Hess, Ortwin
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)