Invention:
This invention relates to methods for improving the properties of photorefractive materials to improve the performance, particularly the grating or image persistency of photorefractive materials. One method is to utilize multiple layers, interposing one or more polymer layers between the transparent electrode layer and the photorefractive material.
Background:
Photorefractivity is a phenomenon in which the refractive index of a material can be altered by changing the electric field within the material, such as by laser beam irradiation. Good photorefractive properties can be seen in materials that combine good charge generation, good charge transport or photoconductivity, and good electro-optical activity. Typically, a high biased voltage is applied to photorefractive materials to obtain good photorefractive behavior. While using a high biased voltage can result in a longer grating persistency, the use of a high voltage in the photorefractive material can cause the photorefractive grating to disappear almost immediately after stopping the applied biased voltage. Therefore, there is a strong need to improve grating holding persistency, even if the biased voltage is stopped and no voltage is being applied.
Advantages:
- Low insertion loss
- Low drive voltage
- High numerical aperture
- Long device lifetime
Applications:
- High density optical data storage
- Dynamic holography
- Optical image processing
- Optical computing
- Phase conjugated mirrors
- Parallel optical logic
- Pattern recognition
Status: Issued U.S. Patent #7,912,327
