<s>
Organic	B-Algorithm
photorefractive	I-Algorithm
materials	I-Algorithm
are	O
materials	O
that	O
exhibit	O
a	O
temporary	O
change	O
in	O
refractive	O
index	O
when	O
exposed	O
to	O
light	O
.	O
</s>
<s>
The	O
buildup	O
can	O
be	O
controlled	O
to	O
produce	O
holographic	B-Algorithm
images	I-Algorithm
for	O
use	O
in	O
biomedical	O
scans	O
and	O
optical	O
computing	O
.	O
</s>
<s>
Addition	O
of	O
impurities	O
into	O
the	O
semiconductor	O
,	O
or	O
doping	B-Algorithm
,	O
produces	O
excess	O
holes	O
or	O
electrons	O
,	O
which	O
,	O
with	O
sufficient	O
density	O
,	O
may	O
pin	O
the	O
Fermi	O
level	O
to	O
the	O
impurities	O
 '	O
position	O
.	O
</s>
<s>
It	O
is	O
only	O
the	O
non-centrosymmetric	O
materials	O
that	O
can	O
exhibit	O
the	O
Pockels	O
effect	O
:	O
for	O
instance	O
,	O
lithium	O
tantalite	O
(	O
trigonal	O
crystal	O
)	O
or	O
gallium	O
arsenide	O
(	O
zinc-blende	O
crystal	O
)	O
;	O
as	O
well	O
as	O
poled	O
polymers	B-Language
with	O
specifically	O
designed	O
organic	O
molecules	O
.	O
</s>
<s>
First	O
photorefractive	O
(	O
PR	O
)	O
effect	O
in	O
organic	O
materials	O
was	O
reported	O
in	O
1991	O
and	O
then	O
,	O
research	O
of	O
organic	B-Algorithm
photorefractive	I-Algorithm
materials	I-Algorithm
has	O
drawn	O
major	O
attention	O
in	O
recent	O
years	O
compare	O
to	O
inorganic	O
PR	O
semiconductors	O
.	O
</s>
<s>
Polymer	B-Language
or	O
polymer	B-Language
composite	O
materials	O
have	O
shown	O
excellent	O
photorefractive	O
properties	O
of	O
100%	O
diffraction	O
efficiency	O
.	O
</s>
<s>
In	O
this	O
way	O
,	O
the	O
polymer	B-Language
also	O
serves	O
as	O
a	O
host	O
matrix	O
to	O
provide	O
the	O
resultant	O
composite	O
material	O
with	O
a	O
sufficient	O
viscosity	O
for	O
reasons	O
of	O
processing	O
.	O
</s>
<s>
The	O
vast	O
majority	O
of	O
the	O
polymers	B-Language
are	O
based	O
on	O
carbazole	O
containing	O
polymers	B-Language
like	O
poly-(N-vinyl carbazole )	O
(	O
PVK	O
)	O
and	O
polysiloxanes	O
(	O
PSX	O
)	O
.	O
</s>
<s>
In	O
polymers	B-Language
,	O
charge	O
is	O
transported	O
through	O
the	O
HOMO	O
and	O
the	O
mobility	O
is	O
influenced	O
by	O
the	O
nature	O
of	O
the	O
dopant	O
mixed	O
into	O
the	O
polymer	B-Language
,	O
also	O
it	O
depends	O
on	O
the	O
amount	O
of	O
dopant	O
which	O
may	O
exceed	O
50	O
weight	O
percent	O
of	O
the	O
composite	O
for	O
guest-host	O
materials	O
.	O
</s>
<s>
Besides	O
the	O
mobility	O
,	O
the	O
ionization	O
potential	O
of	O
the	O
polymer	B-Language
and	O
the	O
respective	O
dopant	O
has	O
also	O
significant	O
importance	O
.	O
</s>
<s>
The	O
relative	O
position	O
of	O
the	O
polymer	B-Language
HOMO	O
with	O
respect	O
to	O
the	O
ionization	O
potential	O
of	O
the	O
other	O
components	O
of	O
the	O
blends	O
determines	O
the	O
extent	O
of	O
extrinsic	O
hole	O
traps	O
in	O
the	O
material	O
.	O
</s>
<s>
As	O
of	O
2011	O
,	O
no	O
commercial	O
products	O
utilizing	O
organic	B-Algorithm
photorefractive	I-Algorithm
materials	I-Algorithm
exist	O
.	O
</s>
<s>
Large	O
DC	O
fields	O
required	O
to	O
produce	O
holograms	B-Algorithm
lead	O
to	O
dielectric	O
breakdown	O
not	O
suitable	O
outside	O
the	O
laboratory	O
.	O
</s>
<s>
Many	O
materials	O
exist	O
for	O
recording	O
static	O
,	O
permanent	O
holograms	B-Algorithm
including	O
photopolymers	O
,	O
silver	O
halide	O
films	O
,	O
photoresists	O
,	O
dichromated	O
gelatin	O
,	O
and	O
photorefractives	O
.	O
</s>
<s>
Updatable	O
holograms	B-Algorithm
that	O
do	O
not	O
require	O
glasses	O
are	O
attractive	O
for	O
medical	O
and	O
military	O
imaging	O
.	O
</s>
<s>
The	O
materials	O
properties	O
required	O
to	O
produce	O
updatable	O
holograms	B-Algorithm
are	O
100%	O
diffraction	O
efficiency	O
,	O
fast	O
writing	O
time	O
,	O
long	O
image	O
persistence	O
,	O
fast	O
erasing	O
time	O
,	O
and	O
large	O
area	O
.	O
</s>
<s>
Liquid	B-Device
crystal	I-Device
3D	O
displays	O
exist	O
but	O
require	O
complex	O
computation	O
to	O
produce	O
images	O
which	O
limits	O
their	O
refresh	O
rate	O
and	O
size	O
.	O
</s>
<s>
Organic	B-Algorithm
photorefractive	I-Algorithm
materials	I-Algorithm
are	O
capable	O
of	O
kHz	O
refresh	O
rates	O
though	O
it	O
is	O
limited	O
by	O
material	O
sensitivity	O
and	O
laser	O
power	O
.	O
</s>
<s>
Phase	O
distortions	O
created	O
by	O
the	O
atmosphere	O
can	O
be	O
corrected	O
by	O
a	O
four-wave	O
mixing	O
process	O
utilizing	O
organic	O
photorefractive	O
holograms	B-Algorithm
.	O
</s>
<s>
Organic	B-Algorithm
photorefractive	I-Algorithm
materials	I-Algorithm
are	O
a	O
nonlinear	O
medium	O
in	O
which	O
large	O
amounts	O
of	O
information	O
can	O
be	O
recorded	O
and	O
read	O
.	O
</s>
<s>
Holograms	B-Algorithm
due	O
to	O
the	O
inherent	O
parallel	O
nature	O
of	O
optical	O
recording	O
are	O
able	O
to	O
quickly	O
process	O
large	O
amounts	O
of	O
data	O
.	O
</s>
<s>
Holograms	B-Algorithm
that	O
can	O
be	O
quickly	O
produced	O
and	O
read	O
can	O
be	O
used	O
to	O
verify	O
the	O
authenticity	O
of	O
documents	O
similar	O
to	O
a	O
watermark	B-General_Concept
Organic	O
photorefractive	O
correlators	O
use	O
matched	O
filter	O
and	O
Joint	O
Fourier	O
Transform	O
configurations	O
.	O
</s>
<s>
High	O
diffraction	O
efficiency	O
allowed	O
a	O
CCD	B-Algorithm
detector	I-Algorithm
to	O
distinguish	O
between	O
light	O
pixels	O
(	O
1	O
bits	O
)	O
and	O
dark	O
pixels	O
(	O
0	O
bits	O
)	O
.	O
</s>
