Browse Prior Art Database

Large Capacity Holographic Memory

IP.com Disclosure Number: IPCOM000077481D
Original Publication Date: 1972-Aug-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Smith, WV: AUTHOR

Abstract

A holographic memory contains the information stored in a stack of equidistantly spaced translucent phase-hologram plates. A polarized tunable laser delivers the interrogation beam, which is directed by a controllable deflector to the addressed area in the hologram plates. Which plate, however, responds to the interrogation beam by backscattering depends on the beam's wavelength. The beam splitter is made unidirectional by the addition of a rotator, such that the backscattered readout beam is directed transversely towards the detector array for interpretation of the output signals. The double concept of access by beam deflection as well as by wavelength tuning permits increased packing density of storage. The memory is practically a read-only memory.

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Large Capacity Holographic Memory

A holographic memory contains the information stored in a stack of equidistantly spaced translucent phase-hologram plates. A polarized tunable laser delivers the interrogation beam, which is directed by a controllable deflector to the addressed area in the hologram plates. Which plate, however, responds to the interrogation beam by backscattering depends on the beam's wavelength. The beam splitter is made unidirectional by the addition of a rotator, such that the backscattered readout beam is directed transversely towards the detector array for interpretation of the output signals. The double concept of access by beam deflection as well as by wavelength tuning permits increased packing density of storage. The memory is practically a read-only memory. Separately prepared hologram plates can be inserted into the hologram stack, whereby the arrangement order can be arbitrarily changed.

On the memory plates of about 10 cm x 10 cm size, each area hit by the interrogating beam contains a small hologram storing of about 10,000 bits. About 10,000 different small holograms are addressable by beam deflection at a plate. About 100 different plates are distinguishable by the light wavelength to which their phase holograms give an answer. Wavelength tuning range spans about 10 to 20 percent. This yields a storage capacity of about 10/10/ bits.

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