<s>
Volume	B-Algorithm
holograms	I-Algorithm
are	O
holograms	B-Algorithm
where	O
the	O
thickness	O
of	O
the	O
recording	O
material	O
is	O
much	O
larger	O
than	O
the	O
light	O
wavelength	O
used	O
for	O
recording	O
.	O
</s>
<s>
In	O
this	O
case	O
diffraction	O
of	O
light	O
from	O
the	O
hologram	B-Algorithm
is	O
possible	O
only	O
as	O
Bragg	O
diffraction	O
,	O
i.e.	O
,	O
the	O
light	O
has	O
to	O
have	O
the	O
right	O
wavelength	O
(	O
color	O
)	O
and	O
the	O
wave	O
must	O
have	O
the	O
right	O
shape	O
(	O
beam	O
direction	O
,	O
wavefront	O
profile	O
)	O
.	O
</s>
<s>
Volume	B-Algorithm
holograms	I-Algorithm
are	O
also	O
called	O
thick	O
holograms	B-Algorithm
or	O
Bragg	O
holograms	B-Algorithm
.	O
</s>
<s>
Volume	B-Algorithm
holograms	I-Algorithm
were	O
first	O
treated	O
by	O
H	O
.	O
Kogelnik	O
in	O
1969	O
by	O
the	O
so-called	O
"	O
coupled-wave	O
theory	O
"	O
.	O
</s>
<s>
For	O
volume	O
phase	O
holograms	B-Algorithm
it	O
is	O
possible	O
to	O
diffract	O
100%	O
of	O
the	O
incoming	O
reference	O
light	O
into	O
the	O
signal	O
wave	O
,	O
i.e.	O
,	O
full	O
diffraction	O
of	O
light	O
can	O
be	O
achieved	O
.	O
</s>
<s>
Volume	O
absorption	O
holograms	B-Algorithm
show	O
much	O
lower	O
efficiencies	O
.	O
</s>
<s>
A	O
good	O
text-book	O
description	O
of	O
the	O
theory	O
of	O
volume	B-Algorithm
holograms	I-Algorithm
can	O
be	O
found	O
in	O
a	O
book	O
from	O
J.Goodman	O
.	O
</s>
<s>
A	O
volume	B-Algorithm
hologram	I-Algorithm
is	O
usually	O
made	O
by	O
exposing	O
a	O
photo-thermo-refractive	O
glass	O
to	O
an	O
interference	O
pattern	O
from	O
an	O
ultraviolet	B-Application
laser	O
.	O
</s>
<s>
It	O
is	O
also	O
possible	O
to	O
make	O
volume	B-Algorithm
holograms	I-Algorithm
in	O
nonphotosensitive	O
glass	O
by	O
exposing	O
it	O
to	O
femtosecond	O
laser	O
pulses	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
a	O
simple	O
Bragg	B-Device
reflector	I-Device
the	O
wavelength	O
selectivity	O
can	O
be	O
estimated	O
by	O
,	O
where	O
is	O
the	O
vacuum	O
wavelength	O
of	O
the	O
reading	O
light	O
,	O
is	O
the	O
period	O
length	O
of	O
the	O
grating	O
,	O
and	O
is	O
the	O
thickness	O
of	O
the	O
grating	O
.	O
</s>
<s>
Considering	O
that	O
because	O
of	O
the	O
Bragg	O
condition	O
the	O
simple	O
relation	O
holds	O
,	O
where	O
is	O
the	O
modulated	O
refractive	O
index	O
in	O
the	O
material	O
(	O
not	O
the	O
base	O
index	O
)	O
at	O
this	O
wavelength	O
,	O
one	O
sees	O
that	O
for	O
typical	O
values	O
(	O
)	O
one	O
gets	O
,	O
showing	O
the	O
extraordinary	O
wavelength	O
selectivity	O
of	O
such	O
volume	B-Algorithm
holograms	I-Algorithm
.	O
</s>
<s>
In	O
the	O
case	O
of	O
a	O
simple	O
grating	O
in	O
the	O
transmission	O
geometry	O
the	O
angular	O
selectivity	O
can	O
be	O
estimated	O
as	O
well	O
:	O
,	O
where	O
is	O
the	O
thickness	O
of	O
the	O
holographic	B-Algorithm
grating	O
.	O
</s>
<s>
Using	O
again	O
typical	O
numbers	O
(	O
)	O
,	O
one	O
ends	O
up	O
with	O
,	O
showing	O
the	O
impressive	O
angular	O
selectivity	O
of	O
volume	B-Algorithm
holograms	I-Algorithm
.	O
</s>
<s>
The	O
Bragg	O
selectivity	O
makes	O
volume	B-Algorithm
holograms	I-Algorithm
very	O
important	O
.	O
</s>
<s>
Distributed-feedback	O
lasers	O
(	O
DFB	O
lasers	O
)	O
as	O
well	O
as	O
distributed-Bragg-reflector	O
lasers	O
(	O
DBR	O
lasers	O
)	O
,	O
where	O
the	O
wavelength	O
selectivity	O
of	O
volume	B-Algorithm
holograms	I-Algorithm
is	O
used	O
to	O
narrow	O
the	O
spectral	O
emission	O
of	O
semiconductor	O
lasers	O
.	O
</s>
<s>
Holographic	B-Algorithm
memory	I-Algorithm
devices	O
for	O
holographic	B-Algorithm
data	I-Algorithm
storage	I-Algorithm
,	O
where	O
the	O
Bragg	O
selectivity	O
is	O
used	O
to	O
multiplex	O
several	O
holograms	B-Algorithm
in	O
one	O
piece	O
of	O
holographic	B-Algorithm
recording	O
material	O
using	O
effectively	O
the	O
third	O
dimension	O
of	O
the	O
storage	O
material	O
.	O
</s>
<s>
Fiber	B-Device
Bragg	I-Device
gratings	I-Device
that	O
employ	O
volume	O
holographic	B-Algorithm
gratings	O
encrypted	O
into	O
an	O
optical	O
fiber	O
.	O
</s>
<s>
Volume	B-Algorithm
holograms	I-Algorithm
are	O
used	O
as	O
tunable	O
optical	O
filters	O
to	O
produce	O
monochromatic	O
images	O
,	O
also	O
known	O
as	O
hyperspectral	B-Application
imaging	I-Application
.	O
</s>
<s>
Low-frequency	O
(	O
"	O
THz	B-Algorithm
"	O
)	O
Raman	B-Algorithm
spectroscopy	I-Algorithm
.	O
</s>
