Tsutomu Ishii

Holographic recording and retrieval of polarized light by use of polyester containing cyanoazobenzene units in the side chain.

We examined the holographic recording properties of polyester containing cyanoazobenzene units in the side chain. It was revealed that, when a linearly polarized object beam with an arbitrary polarization direction was recorded, the retrieved beam had the same polarization state as that of the object beam, with a constant diffraction efficiency of 0.1. Moreover, two object beams with mutually orthogonal linear polarization could be recorded and retrieved separately from the same area. This is, to our knowledge, the first example of holographic polarization multiplexing. The retrieved images were found to resolve details of ~40line pairs/mm and a 40-mum -pitched checkerboard pattern. The resolution of the system is limited by the CCD cameras that are used. Polarization encoding to increase the storage capacity and (or) the signal-to-noise ratio of holographic data recording is also discussed.

23.3: A Novel Photoaddressable Electronic Paper Utilizing Cholesteric LC Microcapsules and Organic Photoconductor

A novel photoaddressable electronic paper has been developed. It has a spatial light modulator (SLM) structure that consists of microencapsulated cholesteric liquid crystal and an organic photoconductive layer between flexible plastic thin films. An A6- size prototype E-Paper sheet exhibits greater than 20% reflectivity, a 4:1 contrast ratio and a wide viewing angle. Images transferred by the projection of a 2D image with a 200 ms electrical pulse exhibit nonvolatility without power and excellent stability against deformation of the sheet.

Digital Data Storage and Computing by a Vector Holographic Memory System

We have applied polarization multiplexing to digital data storage and logic operation. Two digital data pages with mutually orthogonal polarization directions were recorded with a reference beam within the same volume of polyester containing cyanoazobenzene units in the side chain. Illuminating the polyester with the reference beam simultaneously yielded the two data pages. The polarization states of the two retrieved images were mutually orthogonal, because the polyester film is capable of recording arbitrary polarization states. Thus, there was no significant cross talk between the two reconstructed data pages. The bit error rates of the two retrieved pages were estimated to be 10-9 and 10-6. Furthermore, by detecting an appropriate polarization component of the diffracted beams, we have successfully obtained subtraction and addition signals between the two multiplexed pages. Since this system is also applicable to logic operation, it would take advantage of the high-density storage, fast transfer rates, and fast processing speeds.

Polarization Encoding for Digital Holographic Storage

We have proposed polarization encoding for digital holographic storage, in which each pixel or bit encodes two orthogonal polarization states, 0 and 90 degrees, corresponding to binary 1 and 0, respectively. We recorded the polarization-encoded page within an azobenzene-containing polyester film that is capable of recording arbitrary polarization states. After retrieval from the hologram, the polarization-encoded page was divided into mutually orthogonal polarization components. The two polarization components had an intrapage variation, and their bit error rates (BERs) were estimated to be 10-3 and 10-5. Subsequently, to remove the intrapage variation, we calculated the difference between the two polarization components. The intrapage variation successfully decreased on the subtraction image, and its BER was improved to 10-7. Therefore, this method is of great use for eliminating intrapage variations on a reconstructed data page.

Optical computing by a vector holographic memory system

We propose what is to our knowledge a novel holographic memory system that is simultaneously applicable to data storage and optical computing. We introduce a polarization-modulated reference beam into holographic recording. A desired spatial-frequency component of an object beam is recorded as a polarization-modulated grating, and the other component is recorded as an intensity-modulated grating. Since the polarization-modulated grating rotates the polarization axis of the incident light by 90 degrees , it is possible to distinguish the desired spatial-frequency component of the retrieved image. Utilizing this property, we have successfully performed spatial-frequency filtering and frequency-selective matched filtering. The system is capable of a variety of optical computations, depending on the design of the polarization modulation.

60.3: High Resolution Electronic Paper Based on LED Print Head Scanning Exposure

The resolution of photo-addressable electronic papers has been limited to 200dpi due to the resolution of conventional optical modulators used for the electronic paper printer. We have realized the scanning exposure printing of the photo-addressable electronic paper and achieved 600dpi resolution with a LED print head.

Spatial-frequency filtering by vector holographic memory system

This new system is capable of recording polarization. For holographic recording and optical computing, we used polarization-modulated reference beams. Detecting polarization components of retrieved signal, we successfully achieved data retrieval and spatial-frequency filtering.