Document Abstract
Wave
equations
describing
the
non-linear
two-beam
coupling
have
been
solved
and
expressions
for
the
gain
of
the
two
beams
in
the
photorefractive
crystals
have
been
derived.
In
case
of
the
degenerate
two
beam
coupling,
the
gain
depends
upon
the
crystal
thickness,
coupling
coefficient,
absorption
coefficient
and
the
input
intensity
ratio.
The
effect
of
these
parameters
on
the
gain
has
been
studied
in
details.
In
case
of
non-degenerate
two-beam
coupling
the
gain
not
only
depends
upon
crystal
thickness,
coupling
coefficient,
absorption
coefficient
and
the
input
intensity
ratio
but
also
on
the
response
time
of
the
pho
torefractive
medium.
This
response
time
is
the
function
of
concentration
ratio.
The
influence
of
oscillation
frequency
shift,
concentration
ratio
on
the
gain
for
the
non-degenerate
two-beam
coupling
has
also
been
studied.