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Browse Prior Art Database

Optical Logic with QCSE Devices and Polarized Light

IP.com Disclosure Number: IPCOM000113047D
Original Publication Date: 1994-Jul-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 110K

Publishing Venue

IBM

Related People

Keyes, RW: AUTHOR

Abstract

The representation of information by the intensity of a light beam suffers from the lack of a convenient standard of signal amplitude that can be established throughout a system. This is accomplished in electrical logic by connection to voltage supplies, which are easily distributed throughout a system by highly conductive wires, and can be used to determine the output voltage of logic circuits. A method of establishing and using a standardized optical representation of information is described here.

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Optical Logic with QCSE Devices and Polarized Light

      The representation of information by the intensity of a light
beam suffers from the lack of a convenient standard of signal
amplitude that can be established throughout a system.  This is
accomplished in electrical logic by connection to voltage supplies,
which are easily distributed throughout a system by highly conductive
wires, and can be used to determine the output voltage of logic
circuits.  A method of establishing and using a standardized optical
representation of information is described here.

      Bits are represented by the two orthogonal directions of
polarization of linearly polarized light in the present logic method.
Direction of polarization offers a less ambiguous representation of
information than intensity of light because polarization is easily
standardized by well-known means, such as with dichroic and
birefringent crystals and sheet polarizers.  The direction of
polarization is also easily recognized by its ability to pass through
such oriented filters.  Herein one direction of linear polarization,
called V, is taken to represent a ONE and the perpendicular
direction, called H, represents a ZERO.  A further advantage of the
representation by polarization is that the operation of inversion or
negation, which is recognized as an essential element of binary
logic, is easily implemented as a 90º  rotation of the direction
of polarization, by a half-wave plate, for example.

      Gain is another necessary ingredient of sequential logic.  The
amplitude of signals must not be allowed to decrease beyond a certain
point.  The same methods that provide gain with unpolarized light are
available with polarized light.  Here a known device and circuit
arrangement based on the Quantum-Controlled Stark Effect (QCSE) is
employed [1,2].  The device of [1]  was called the SEED (Self
Electro-optic Effect Device) and the circuit in which it is used the
S-SEED (Symmetric SEED).  The circuit provides "time-sequential
gain", as explained by [1].

      The S-SEED is illustrated in part (a) of the Figure, in which
the SEED devices are represented by rectangles 10 and 11.  The basis
of the circuit is that the devices have a negative resistance and the
series combination of them forms a bistable circuit.  Most of the
voltage applied to the circuit appears across one or the other of the
devices in a static condition.  The device that supports the voltage
is relatively transparent and the low-voltage device is opaque to
light of a certain wavelength.  The devices are also photoconductive;
when light is incident on a device that is supporting a high voltage
the light-induced conductivity causes the voltage to fall and the
circuit to switch to the state in which the other device supports the
voltage, and thereby becomes transparent.  In summary, then, the
state of the circuit can be changed by optical inputs and the state
can be det...