Fai H. Mok

System metric for holographic memory systems

We introduce M/# as a metric for characterizing holographic memory systems. M/# is the constant of proportionality between diffraction efficiency and the number of holograms squared. Although M/# is a function of many variables in a holographic recording system, it can be measured from the recording and erasure of a single hologram. We verify experimentally that the diffraction efficiency of multiple holograms follows the prediction of M/# measured from a single hologram.

Optically programmable gate array

The Optically Programmable Gate Array (OPGA), an optical version of a conventional FPGA, benefits from a direct parallel interface between an optical memory and a logic circuit. The OPGA utilizes a holographic memory accessed by an array of VCSELs to program its logic. An active pixel sensor array incorporated into the OPGA chip makes it possible to optically address the logic in a very short time allowing for rapid dynamic reconfiguration. Combining spatial and shift multiplexing to store the configuration pages in the memory, the OPGA module can be made compact. The reconfiguration capability of the OPGA can be applied to solve more efficiently problems in pattern recognition and database search.

Optical memory for computing and information processing

The high data transfer rate achievable in page-oriented optical memories demands for parallel interfaces to logic circuits able to process efficiently the data. The Optically Programmable Gate Array, an enhanced version of a conventional FPGA, utilizes a holographic memory accessed by an array of VCSELs to program its logic. Combining spatial and shift multiplexing to store the configuration pages in the memory, the OPGA module is very compact and has extremely short configuration time allowing for dynamic reconfiguration. The reconfiguration capability of the OPGA can be applied to solve more efficiently problems in pattern recognition and digit classification.

Optically reconfigurable processors

Reconfigurable processors bring a new computational paradigm where the processor modifies its structure to suit a given application, rather than having to modify the application to fit the device. The Optically Programmable Gate Array, an enhanced version of a conventional FPGA, utilizes a holographic memory accessed by an array of VCSELs to program its logic. Combining spatial and shift multipexing to store the configuration pages in the memory, the OPGA module is very compact and has extremely short configuration time allowing for dynamic reconfiguration. The reconfiguration capability of the OPGA can be applied to solve more efficiently problems in pattern recognition and digit classification.

Angle and space multiplexed holographic storage using the 90" geometry

The 90-degrees geometry - with reference and signal beams entering orthogonal crystal faces - is used to angularly multiplex up to 500 holograms at each of 8 spatially multiplexed locations in a LiNbO3 crystal. A segmented mirror array and a 2D mechanical scanner are used to perform both angular and spatial multiplexing. We show that this mirror array can be used with non-mechanical angle scanners, providing for holographic storage in multiple locations with no moving parts.

Large-scale volume holographic storage in the long interaction length architecture

We describe a page-formatted random-access holographic memory designed to store up to 160,000 holograms. The memory consists of 16 vertically spaced locations, each containing 10,000 holograms, which in turn are organized as 10 fractal-multiplexed rows of 1000 angularly-multiplexed holograms. A segmented mirror array is used to enable random access to any of the stored holograms within the access time of a non-mechanical angle scanner such as an acousto-optic deflector. Using a mechanical scanner with such a mirror array, we demonstrate storage of 10,000 holograms at a single location of the system, as well as simultaneous storage and recall of holograms at 6 locations, including the highest and lowest of the 16 locations.

Spatially and angle-multiplexed holographic random access memory

A 3-D holographic optical memory is described that combines spatially and angularly multiplexed storage to yield a storage capacity of approximately 1012 bits in a crystal with volume less than 100 cm3. A non-mechanical scanning mechanism, consisting of acoustooptic deflectors and a segmented mirror, retrieves any stored hologram in a time equal to the acoustic delay through the aperture of the acoustooptic deflector.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Large-scale rapid access holographic memory

We describe a page-formatted random-access holographic memory capable of storing up to 160,000 holograms. A segmented mirror array allows a 2D angle scanner to provide access to any of the stored holograms. High-speed random access can be achieved with a nonmechanical angle scanner. We demonstrate holographic storage and high-speed retrieval using an acousto- optic deflector.

Holographic optical disc

The holographic disc is a high capacity, disk-based data storage device that can provide the performance for next generation mass data storage needs. With a projected capacity approaching 1 terabit on a single 12 cm platter, the holographic disc has the potential to become a highly efficient storage hardware for data warehousing applications. The high readout rate of holographic disc makes it especially suitable for generating multiple, high bandwidth data streams such as required for network server computers. Multimedia applications such as interactive video and HDTV can also potentially benefit from the high capacity and fast data access of holographic memory.

Large-Scale Holographic Memory - Experimental Results

We present experimental results of a page-formatted random-access holographic memory capable of storing up to 1012 bits of information. Up to 500 holograms were angularly multiplexed at each of 8 spatially multiplexed locations, using a mechanical scanner and a segmented mirror array.