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Nonlinear Optics and Laser Physics:
Slow
Light via Stimulated Brillouin Scattering in Optical Fibre
Recently it has been established
that the alteration of the propagation velocity of light pulses by light,
i.e. so called “slow light” phenomenon, offers the possibility to develop
systems such as optical delay lines,
optical buffers, optical equalizers and signal processors. These devices
can be used to build transparent all-optical networks, that will
undoubtedly be the future of telecommunication systems.
One of the most actively
investigated technique to achieve “slow” light is based on the nonlinear
effect of stimulated Brillouin scattering. In this process a Stokes
shifted scattered wave is amplified in an optically transparent medium by
parametric coupling with an incident (pump) wave and a material (acoustic)
wave in the medium. Here the gain profile and its associated dispersion are
used to achieve high group index of optical pulses. For generating slow
light, a pump signal, usually continuous wave is used to prime the gain
process which is probed by a counter-propagating pulsed signal tuned to the
Stokes frequency. Along with obvious device compatibility, there are
several other advantages of this approach for optical communications
systems: the slow-light resonance can be created at any wavelength by
changing the pump wavelength; the use of optical fibre allows for long
interaction lengths and thus low powers for the laser beams, the process is
run at room temperature, it is simple and easy to handle, besides off the shelf telecom equipment
can be used, and SBS works in the fibers entire transparency range and in
all types of fibers.
This combined theoretical and
experimental program addresses the fundamentals of slow light generation in
fiber-based SBS along with its application for data rate transmission at
Gb/s rates for telecommunications. Specifically such high data rates will
take advantage of the phenomenon of waveguide induced spectral broadening.
Through this phenomenon the spectral bandwidth of SBS may be broadened to
GHz in conventional fiber and to
tens of GHz on photonic crystal fiber, the latter of which is developed by
the group of Prof. Knight at Bath
University, our
collaborators on this program. Fundamental issues address the implications
of the built-up time of SBS on slow light, the role of spontaneous
Brillouin scattering and its amplification on invoking controllable delay
in slow light and the basic science of SBS in photonic crystal fibers. In
experiments we use
frequency-stabilized CW-Nd:YAG lasers as the workhorse for
generating for generating slow light via SBS in this fiber systems.
Research
areas:
·
Nonlinear dynamics
of SBS
·
Multi-mode
nonlinear coupling of SBS
·
Stochastic origin
of SBS
·
Inhomogeneous
spectral broadening of SBS
·
Application:
all-optical networks.
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