Browse Prior Art Database

Implementation of a Storage Device using Persistent Spectral Hole-Burning

IP.com Disclosure Number: IPCOM000117055D
Original Publication Date: 1995-Dec-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 123K

Publishing Venue

IBM

Related People

Jefferson, M: AUTHOR [+3]

Abstract

The idea that Persistent Spectral Hole-burning could be used to make a storage device is contained in (1). The basic concept was that information could be stored by associating data bits with wavelength dependent spectral features written into the absorption line of a material at low temperature. Conceptually, many (1000 to greater than 10,000) bits could be written in a single spot, increasing the storage density manyfold. Such a scheme is detailed in (2). An advantage of this sort of data storage scheme is that it has the potential for allowing a mass storage device with no moving parts. A disadvantage of the "many bits per spot" approach is the technological difficulty of either accessing the exact spot precisely or detecting the bits with low error rate when the laser is scanned over the absorption line.

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Implementation of a Storage Device using Persistent Spectral Hole-Burning

      The idea that Persistent Spectral Hole-burning could be used to
make a storage device is contained in (1).  The basic concept was
that information could be stored by associating data bits with
wavelength dependent spectral features written into the absorption
line of a material at low temperature.  Conceptually, many (1000 to
greater than 10,000) bits could be written in a single spot,
increasing the storage density manyfold.  Such a scheme is detailed
in (2).  An advantage of this sort of data storage scheme is that it
has the potential for allowing a mass storage device with no moving
parts.  A disadvantage of the "many bits per spot" approach is the
technological difficulty of either accessing the exact spot precisely
or detecting the bits with low error rate when the laser is scanned
over the absorption line.  The scanning will produce a very messy
signal in which small intensity variations (representing bits) are
impressed on a large and varying signal due to the shape of the
absorption line as a function of wavelength.  This signal will be
very hard to process in a way as to yield acceptable error rates.  In
addition, the rate at which data may be written or read is limited by
the linewidth of the spectral holes, which in some cases would make
the achievable data rate unacceptably slow.

      Instead of thinking in terms of "bits per spot", it is
necessary to regard each discrete interval of wavelength over which
identifiably separate "bits" could be written as a fresh "page" onto
which data can be written.  Thus, a thin layer of PSHB material would
comprise a multiplicity of separate and distinct "surfaces", each
corresponding to a different wavelength interval, onto which data
could be written.

      Using this scheme, data could be written onto a "page" or
"surface" by fixing the wavelength of the laser and scanning the beam
spatially, modulating the intensity as required.  Thus an entire
record or set of records could be written at a single wavelength.
Because the records are written at fixed laser frequency, the
readback process is simplified.  Rather than sweeping the laser
frequency, the laser is fixed at that frequency which corresponds to
the desired record and then spatially scanned.  The resulting change
of intensity due to the absorption modulation is superimposed on a
relatively constant background intensity.  This avoids the previously
mentioned problem of finding the bits in a rapidly varying background
signal.  Using this technique, synch bytes and record headers may be
written on each record, as is done with magnetic and magneto-optical
recording.  These bookkeeping bits would restrict the use of the
conventional "bits per spot" scheme due to the fact that the
multiplicity of bits which can be stored as a function of wavelength
is limited and thus the bookkeeping bits subtract from the total
number of data bits...