Systems and Methods for Improving the Performance of a Photorefractive Device

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Nasser Peyghambarian
Professor, Optical Sciences
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Amy Phillips
Sr. Licensing Manager (520) 621-9579
Patent Protection
US Patent 8,203,780

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. The change of the refractive index is achieved by a series of steps, including: (1) charge generation by laser irradiation, (2) charge transport, resulting in the separation of positive and negative charges, (3) trapping of one type of charge (charge delocalization), (4) formation of a nonuniform internal electric field (space-charge field) as a result of charge delocalization, and (5) refractive index change induced by the non-uniform electric field. Therefore, good photorefractive properties can generally be seen in materials that combine good charge generation, good charge transport or photoconductivity, and good electro-optical activity. In recent years, efforts have been made to optimize the properties of organic, and particularly polymeric, photorefractive materials. Good photorefractive properties depend upon good charge generation, good charge transport, also known as photoconductivity, and good electro-optical activity. Various studies have been performed to examine the selection and combination of the components that give rise to each of these features. Typically, a high biased voltage can be applied to photorefractive materials in order 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.

Invention: The present disclosure provides a method for improving the performance of a photorefractive device comprising one or more transparent electrode layers and a photorefractive material. The method comprises interposing one or more polymer layers between the transparent electrode layer and the photorefractive material. In an embodiment, the peak diffraction efficiency bias of the photorefractive device after incorporating the one or more polymer layers in the photorefractive device is reduced when measured by using an approximately 532 nm laser beam, relative to a photorefractive device containing at least one transparent electrode layer and a photorefractive material without a polymer layer interposed there between.

Application: This technology and its chemical compounds can be used to improve photorefractivity by reducing the peak diffraction efficiency bias. It could be incorporated into improving semiconductors and into replacing current polymers in numerous application while reducing power consumption and increasing shelf life.

Advantages:

This invention has been demonstrated to be superior to the state-of-the-art in (a) theory, (b) simulations, and © using real data. Our simulation results show orders of magnitude in improvement, as compared to traditional methods. Real results from data closely replicate the performance of our simulations.

  • grating persistency of the photorefractive device comprising a polymer layer can be extended
  • and held for long period of time,
  • In an embodiment, 90% of the grating remains even after 60 hours storage of the photorefractive device.
  • Polydioxaborine layers can be used for higher grating preservation

Lead Inventor: Nasser N. Peyghambarian

Status:  This invention issued as US Patent No.:  8,203,780 on 6/19/2012. The patent is currently under exclusive option which expires on 11/01/2014. Interested parties should contact the University of Arizona for further information.

UA ID:  UA10-027