We discuss a volume optical storage, a 3D memory based on two-photon absorption process. This memory has an advantage over a 2D memory in that it combines fast access time together with high memory capacity--a capability that 2D memories cannot deliver. Two-photon 3D memory allows the data to be accessed in parallel, and thus speeds up data transfer rate significantly. In this paper, we address the issue of memory hierarchy which has been organized to provide a performance continuum of different memory technologies available at present. We justify the two-photon 3D memory as a viable technology to fill the performance gap currently exists between a primary and secondary storage systems. We also discuss the system capacity pertaining to two unique addressing schemes, i.e., orthogonal beam addressing and counterpropagating beam addressing. Finally, we report the progress in system study regarding the effect of memory material characteristic to the system design and development. Factors such as optimum wavelengths for read/write operations, material fluorescence, material fatigue, and the concentration of active molecules in the host material were considered.
We describe progress in developing a 3D optical memory using 2 photon optical recording. The memory can be designed for bit, line, or page oriented data storage. We discuss advantages and drawbacks to each addressing method in terms of the capacity, storage density, and peripheral devices. We conclude with the most recent experimental results for multiple image storage using 2-photon recording.
We have been developing a two-photon 3-D memory expected to provide a Tbit storage capacity and a 1 ms access time for secondary storage. Even with this new technology, there still exists a four order of magnitude gap in access times between electronic RAMS and secondary storage. In addition to the existing permanent storage approach, we have begun working on systems, key components, and materials for a dynamic parallel-access 3-D two photon memories that will bridge the gap in primary memory technologies. Over the past three years our team has been developing a write-once mass-storage memory based on two-photon bond dissociation of spirobenzopyran molecules for long lifetime storage. A cache memory must have fast write-erase capability. To achieve this we are beginning to investigate highly sensitive two-photon materials which spontaneous decay (self-erase) to the off state. These materials will be incorporated into dynamic memory systems which continually refresh the memory contents, as in an electronic DRAM. The resulting memory is expected to provide a data capacity of 1 Gbit/cm3 with a 10 ns to 1 microsecond(s) access time and a 10 Tbit/s data rate. In this presentation the latest results of the parallel-access 3-D volume memory using two-photon storage is discussed. We cover material and system considerations for both types of parallel-access memories: fast-access primary storage and large-capacity secondary storage.
The computational power of current high-performance computers is increasingly limited by data storage and recall rates. In existing sequential-access electronic memories, a hierarchy of devices from cache memory to secondary storage provides a performance continuum, allowing a balanced system design. Here we discuss the use of 3-D volume storage based on two photon materials to bridge the gaps in the storage hierarchy of parallel-access memories.
We present the design, implementation and performance of a holographic dynamic focusing lens (HDFL). This device was developed to focus a 2D array of point sources to any of the many discrete planes inside the volume memory material. The lens utilizes two components: a spatial light modulator (SLM) as an active element which allows fast switching (≈ 1 μsec), and a diffractive optical element which allows for high SBP. The unique design feature of this device is that the resolution of the lens is not dependent on the resolution of the SLM. Simulation and experimental results are presented.
The computational power of current high-performance computers is increasingly limited by data storage and retrieval rates rather than the processing power of the central processing units. No single existing memory technology can combine the required fast access and large data capacity. Instead, a hierarchy of serial access memory devices has provided a performance continuum which allows a balanced system design. Conventional memory technology can only marginally support the needs of high performance computers in terms of required capacity, data rates, access times and cost. Significant gaps in secondary and tertiary storage have emerged which make storage hierarchy design increasingly difficult. This paper reviews a radically different approach to data storage using the parallelism and three dimensionality of optical storage. 3-D optical storage has the potential to significantly alter the present hierarchy and fill the pressing need for high performance secondary and tertiary storage systems.
KEYWORDS: Molecules, Computing systems, Gallium arsenide, Photons, Magnetism, 3D optical data storage, Data storage, Spatial light modulators, Signal processing, Absorption
A new type of memory device is presented which takes advantage of the volume of a storage material in order to achieve extremely high information density and capacity. The unique properties of two-photon materials allows for reading and writing to any localized region throughout the volume of material. In addition to the high capacity the 2-photon 3-D memory system has been designed to access up to 106 bits in a single clock cycle. This large parallelism combined with an access time of 1/1 sec gives a memory bandwidth of 1012 bits/sec. It is shown that this value of memory bandwidth far exceeds that available from current memory systems and therefore is well-suited for the demands of current and future supercomputing systems. 1.
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