The document discusses various hologram recording media, including their properties and suitability for recording holograms. It describes silver halide photographic emulsion, dichromated gelatin, photoresist, photopolymer, photochromic, photothermoplastic, and photorefractive crystal recording materials. For each material, it provides details on composition, sensitivity, resolution, diffraction efficiency, and suitability for transmission or reflection holograms.

1. HOLOGRAM RECORDING MEDIUM
BY – ADITYA NARAYAN SINGH
IMSC PHYSICS 2017
BIRLA INSTITUTE OF TECHNOLOGY
TO – DR KINGSUKE BOSE
ASSISTANT PROFESSOR
BIRLA INSTITUTE OF TECHNOLOGY

2. These are the known recording medium
 Silver halide photographic emulsion
 Dichromated Gelatin
 Photoresist
 Photopolymer
 Photochromics
 Photo thermoplastic
 Photorefractive Crystal

3. SILVER HALIDE PHOTOGRAPHIC EMULSION
 More like conventional and normal
recording medium
 High sensitivity, commercially available and
uses most of the common laser.
 Gain is 106 but need wet processing and
drying.
 Delay in processing leads to fading of
latent image.
 Max diffraction efficiency at OD of 0.7 
transmission hologram
 Max diffaraction efficiency at OD of 2.0 
reflection hologram
 Latent image formation and development

4. DICROMATED GELATIN
1. Considered to be ideal material for volume phase
hologram recording, it has large refractive index
modulation high resolution and low absorption and
scattering . Hologram recording in DCG is based on
the fact that small amount of dichromate such as
(NH4)2Cr2O7 becomes progressively harder when
exposed to light , it is due to formation of cross links
between two or more gelatin by photochemically
produced Cr3+ ions.
2. DCG has excellent resolution & MTF ( SP of 5000
mm-1 ) suitable for both reflection and transmission
hologram. RI modulation is of about 0.08 with very
low scattering possible .

5. Photoresist
1. These are the organic films , gives relief image after exposure
and development, photoresist are usually coated on glass(2
micron think, baking at 75 centigrade)
2. Photoresist are relatively slow , requiring an exposure of 102
J/m2 to blue light 450 nm. They give thin phase hologram
therefore get affected by non linear nature at higher
diffraction efficiency .
3. Two types of photo resist are there positive and negative.
4. Most used photoresist is Shipley AZ-1350, which is most
sensitive in ultraviolet region. So, best hologram is recorded
with Argon ion laser or He-Cd laser.

6. Photopolymer
 Photo polymers are materials which are activated through a photo sensitizer to
exhibit thickness and RI varies due to polymerization. Thick layer are made to
give volume phase hologram with high diffraction efficiency. After exposure
continuous dark reaction due to diffusion increases the RI modulation.
 Two photo polymers are available first, Polaroid DMP 128 and Du Pont OmniDex
polaroid 128 uses dye sensitized photopolymerization of vinyl monomer which is
coated on glass or plastic substrate.
 Du OmniDex consist of polyester based film coated with a photopolymer layer
and thin layer is removable & limited on to a tacky photopolymer layer. Hologram
is recorded usually by contact copying a master hologram , as it require high
energy exposure then UV exposure and then baking.

7. Photochromic
 Undergoes some changes in color, two types , organics and inorganics but organic
photochromics are prone to fatigue .
 They follow a process called photochromism and it is due to reversible charge transfer
between two species of electron traps .
 We have photodichromic, absorption centers are anisotropic and selective alignment of
these centers is induced by exposure to linearly polarized light , it has higher sensitivity of
(exposure 102 J/m2)
 Inorganic photochromics are grain free & have high resolution, more number of hologram
can be recorded , they do not require processing and can be erased and reuse for infinite
times. (But diffraction efficiency < 0.02 & sensitivity is low)

8. Photo thermoplastic
1. Once the thermoplastic layer is cooled , so
the thickness variation is frozen and
hence the hologram become quite stable.
1. Also for development we can use solvent
vapor to soften the thermoplastic so need
of heating is eliminated , again this
method of development gives higher
sensitivity and low noise .
1. After second charging latent image is
insensitive to light exposure so possibly
we can monitor the diffraction efficiency
of hologram during the process of
development

9. Photorefractive Crystal
1. Due to diffusion of trapped electron and
internal photovoltaic effect a space charge
pattern is created , due to this we can see
electro optic effect and refractive effect
modulation pattern and this result in volume
phase hologram.
2. Good diffraction efficiency , higher angular
sensitivity so large number of hologram.
3. Few examples of these materials are Fe
doped LiNbO3 , Bi12SiO20 (BSO), Bi12GeO20
(BGO).
4. Images can be read out for large time , can
generate phase conjugate wavefront and is
used in real – time interferometry.

10. Finally we have this table as summary of Recording
Materials

11.  Optical Holography, principles , techniques and application by
P
. Hariharan
 Google.com/Wikipedia
 Wallpaper-hd.com
 Personal class notes