Dynamics of Partially Coherent Solitons
Principal Investigator
Darran Edmundson
Optical Sciences Centre Research School of Physical Sciences and Engineering
Co-Investigators
Nail Akhmediev
Ole Bang
Optical Sciences Centre
Research School of Physical Sciences and Engineering
Wieslaw Krolikowski
Laser Physics Centre Research School of Physical Sciences and Engineering
Project
x12 - VPP
A ray of light refracts towards the normal as it enters
a medium having a higher refractive index. This
phenomena is exploited in optical fibers where laser pulses are transversely
confined by the relatively higher refractive index in the fiber core. The
optimal index profile is selected by design and then the "waveguide"
is permanently fixed in the glass during fabrication.
In the presence of intense laser light, the refractive index of many nonlinear
materials increases in proportion to the light intensity. Thus, one can
imagine a suitably shaped beam travelling through an otherwise uniform index
block and inducing its own optical waveguide. Such a self-trapped beam is
known as a spatial soliton. Over the last decade spatial solitons have been
studied extensively in view of their potential for realizing all-optical
photonic devices.
While work in the field to date has focused on coherent solitons, recent
experiments with photorefractive crystals have renewed theoretical interest
in the physics of incoherently coupled beams. The overall aim of our project
is quite general: to understand the effect of incoherence on the propagation
of 2-dimensional beams in nonlinear bulk media. Our mathematical model consists
of an infinite number of 2D nonlinear Schroedinger (NLS) equations coupled
to the refractive index potential induced by the total beam intensity.
What are the results to date and the future of the work?
Much of 1998 was spent in developing, debugging and testing of a robust numerical code; only in the last quarter have we finally begun production simulations. With the integrity of the solver now established, we are investigating how the power threshold for collapse of a 2D Gaussian beam is affected by beam coherence. We plan to continue with these dynamical studies as well as initiate a search for stable beams in saturable nonlinear media.