Compact Holographic Data Storage

Introduction: NASA’s future missions would require massive high-speed onboard data storage capability to Space Science missions. For Space Science, such as the Europa Lander mission, the onboard data storage requirements would be focused on maximizing the spacecraft’s ability to survive fault conditions (i.e. no loss in stored science data when spacecraft enters the “safe mode”) and autonomously recover from them during NASA’s long-life and deep space missions. This would require the development of non-volatile memory. In order to survive in the stringent environment during space exploration missions, onboard memory requirements would also include: survive a high radiation environment (1 Mrad), operate effectively and efficiently for a very long time (10 years), and sustain at least a billion (10) write cycles. Therefore, memory technologies requirements of NASA’s Earth Science and Space Science missions are: large capacity, nonvolatility, high-transfer rate, high radiation resistance, high storage density, and high power efficiency. JPL, under current sponsorship from NASA Space Science and Earth Science Programs, is developing a highdensity, nonvolatile and rad-hard Compact Holographic Data Storage (CHDS) system to enable largecapacity, high-speed, low power consumption, and read/write of data in a space environment. The entire read/write operation will be controlled with electrooptic mechanism without any moving parts. This CHDS will consist of laser diodes, photorefractive crystal, spatial light modulator, photodetector array, and I/O electronic interface. In operation, pages of information would be recorded and retrieved with random access and high-speed. The nonvolatile, rad-hard characteristics of the holographic memory will provide a revolutionary memory technology meeting the high radiation challenge facing the Europa Lander mission. CHDS System Architecture And Recent Progress: The CHDS architecture, under development at JPL, as shown in Figure 1, consists of a writing module for multiple holograms recording and a readout module for hologram readout. The writing module include a laser diode as the coherent light source, a pair of cascaded beam steering Spatial Light Modulators (BSSLM), one transmissive and one reflective in each pair, for angular multiplexed beam steering, an input SLM for electronic-to-optical data conversion and a photorefractive crystal for hologram recording and storage. The readout module includes a laser diode with the same wavelength as the writing one, a pair of cascaded BSSLMs to generate phase conjugated readout beam (i.e. the readout beam is directed in opposite direction of that of the writing beam and a photodetector array for recording the readout holograms. The system uses angle multiplexing scheme to store multiple holograms and phase-conjugated beams to readout each hologram.