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Nonlinear Optics and Laser Physics:
Optical
Fibre Phase Conjugation
It has been known since the early 70’s that stimulated Brillouin
scattering (SBS), through its self-phase conjugate (SPC) properties,
provides an effective means for beam clean up of moderate to high power
pulsed lasers. Optical fibre
technology has opened up the new possibility for extending the method of
SPC through SBS to CW laser sources.
This offers an attractive approach for generating power scalable,
diffraction limited outputs based on rugged and inexpensive state of the
art fibres. Our group pioneered this
field with the successful demonstration of high fidelity, polarised SPC of
CW and also long pulse laser radiation in multi mode optical fibre, and
from this the generation of diffraction limited output in a test of
principle CW Nd:YAG master oscillator/power amplifier (MOPA). These developments are the basis for now
taking our research through, in collaboration with QinetiQ, to a real
application of this new technology for beam clean up of a high power diode
pumped Nd:YAG MOPA, and extension of the technology to the new and
challenging areas of high power all-diode and all-fibre MOPAs.
The motivation of this work is for the development of these sources
for broad ranging industrial applications: material processing,
communication and remote sensing, visual displays and large screen
projection, to name a few. Specific
to material processing, high power diffraction limited beam quality is
critical for efficient and high-resolution laser cutting and drilling. On the other hand multi-watt diffraction
limited sources from all-diode and fibre laser systems are key to future
optical communication and opto-electronic technology.
Most recently we have discovered
the phenomenon of spectral phase self-conjugation in SBS. This work has
shown it to be a generic property of stimulated scattering and is the
direct spectral/temporal counterpart
to spatial phase conjugation,
considered above. It offers a unique means of restoring temporal coherence
of optical radiation.
Research
areas:
·
Power-scaling
capability of fibre SPC mirror.
·
Application of
fibre SPC mirror for beam clean-up of
o
high power (~ kW)
diode pumped Nd:YAG MOPA system (with QinetiQ).
o
multi-watt CW
all-diode MOPA.
o
multi-watt CW
all-fibre MOPA.
·
Fundamentals of
spectral self phase conjugation.
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