Organic photorefractive materials
[4] Photoconductivity is the property of a material that describes the capability of incident light of adequate wavelength to produce electric charge carriers.
[6] A sufficiently energetic light can excite charge carriers so much that they will populate the initially empty localized levels.
The dark conductivity of such a material is given by where σd is the conductivity, e = elementary charge, Nd and N+d are the densities of total photoactive centers and ionized empty electron acceptor states, respectively, β is the thermal photoelectron generation coefficient, μ is the mobility constant and τ is the photoelectron lifetime.
Essentially, the Pockels effect is the change of the material's refractive index induced by an applied electric field.
At a microscale, such a decrease occurs because of a disturbance in the charges of each atom after being subjected to the electromagnetic field of the incident light.
The refractive index change will be proportional to the square of the electric field strength and will therefore be much weaker than the Pockels effect.
This is due to mainly cost effectiveness, relatively easy synthetic procedure, and tunable properties through modifications of chemical or compositional changes.
Most recently, amorphous composites of low glass transition temperature have emerged as highly efficient PR materials.
In this way, the polymer also serves as a host matrix to provide the resultant composite material with a sufficient viscosity for reasons of processing.
The relative position of the polymer HOMO with respect to the ionization potential of the other components of the blends determines the extent of extrinsic hole traps in the material.
Large DC fields required to produce holograms lead to dielectric breakdown not suitable outside the laboratory.
Many materials exist for recording static, permanent holograms including photopolymers, silver halide films, photoresists, dichromated gelatin, and photorefractives.
[16] Inorganic materials capable of rapid updating exist but are difficult to grow larger than a cubic centimeter.
Liquid crystal 3D displays exist but require complex computation to produce images which limits their refresh rate and size.
Phase distortions created by the atmosphere can be corrected by a four-wave mixing process utilizing organic photorefractive holograms.
[22] Holograms due to the inherent parallel nature of optical recording are able to quickly process large amounts of data.
Holograms that can be quickly produced and read can be used to verify the authenticity of documents similar to a watermark[22] Organic photorefractive correlators use matched filter[23] and Joint Fourier Transform[24] configurations.
