Document Abstract
Frequency
detuning
dependence
of
four-beam
coupling
in
a
photorefractive
crystal
pumped
with
two
counter-propagating
waves
for
a
semilinear
coherent
optical
resonator
on
the
oscillation
conditions
has
been
analyzed
in
the
case
of
non-degenerate-wave
mixing
under
the
slowly
varying
amplitude
approx
imation
method.
Self
oscillation
can
be
achieved
when
the
gain
arising
from
the
four-beam
coupling
is
large
enough
to
overcome
the
cavity
loss.
The
effects
of
frequency
detuning
(i.e.,
non-degeneracy),
dielectric
constant
and
photoconductivity
of
the
photorefractive
materials
on
the
performance
of
the
semilinear
photorefractive
coherent
resonator
with
the
reflection
grating
configuration
have
also
been
studied
in
detail.
The
phase-conjugate
reflectivity
of
the
pumped
crystal
and
oscillation
intensity
has
been
calculated
for
different
input
pump
beam
intensity
ratio,
intensity
reflectivity
of
the
conventional
mirrors,
degenerate
energy
coupling
strength
of
the
interacting
beams.
It
has
been
found
that
for
the
higher
value
of
the
photoconductivity
p(>2.0
pS/cm)
of
photorefractive
crystal,
the
semilinear
resonator
can
oscillate
at
almost
any
frequency
detuning
(˝)
of
the
oscillation
beam
with
respect
to
the
fixed
fre
quency
of
the
pump
waves
whereas
for
the
lower
value
of
photoconductivity
p(<0.1
pS/cm)
oscillation
occurs
only
when
the
frequency
detuning
is
limited
to
small
region
around
˝
=
0.
But
reverse
of
the
case
is
found
for
dielectric
constant
(ε),
pump
intensity
ratio
(p)
and
conventional
mirror
reflectivity