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Two-Wavelength Phase-Change

IP.com Disclosure Number: IPCOM000099140D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-14
Document File: 4 page(s) / 104K

Publishing Venue

IBM

Related People

Nelson, DQ: AUTHOR

Abstract

One technology being considered for a rewritable disk is "phase-change recording". This technology an advantage over magneto-optic recording for two 1. Only a single revolution is required to write improving performance. 2. No bias coil is needed, therefore reducing the cost.

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Two-Wavelength Phase-Change

       One technology being considered for a rewritable disk is
"phase-change recording".  This technology an advantage over
magneto-optic recording for two
 1.  Only a single revolution is required to write improving
     performance.
 2.  No bias coil is needed, therefore reducing the
     cost.

      The standard phase-change recording method uses a disk an
active layer that exists in two phases or states 1):
   1.  Crystalline State--High Reflectivity
   2.  Amorphous State--Low Reflectivity

      The amorphous state is changed to the crystalline state slowly
heating an area of the active layer with a long, low power laser
pulse.  The structure of active layer is given sufficient time to
obtain a state by cooling slowly.

      The amorphous state is created by quickly heating a area of the
active layer.  The crystalline area is to a near molten state and
then cooled very quickly heat conduction into the surrounding
substrate.  The cooling of the active medium does not allow it to to
a crystalline state, and thus the phase is changed amorphous.

      The media is then read using a very low power laser and the
reflectance of the media using amplitude techniques.

      This technology requires a difference in the pulse for writing
amorphous and crystalline areas.  The of the pulse widths is about
10:1 for amorphous to  A state-of-the-art disk requires a pulse width
about 50 nanoseconds for the amorphous state and 5 for the
crystalline state.  The bits on the will therefore be spaced at least
50 nanoseconds which limits the data rate of the technology (Fig.

      The problem of long pulse widths for the creation of the area
on the phase-change material can be by using a different write
process.  The media is by adding a secondary substrate, just above
and to the active phase-change layer.  This substrate made...