Browse Prior Art Database

Logic and Memory Apparatus

IP.com Disclosure Number: IPCOM000093388D
Original Publication Date: 1967-Sep-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 3 page(s) / 52K

Publishing Venue

IBM

Related People

Chang, PT: AUTHOR [+2]

Abstract

Sequential and combinatorial logic and information storage are accomplished utilizing the inverse Faraday effect. This effect occurs when circularly polarized light is incident on a nonabsorbing crystal, such as europium calcium fluoride, inducing a magnetic moment in the crystal.

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Logic and Memory Apparatus

Sequential and combinatorial logic and information storage are accomplished utilizing the inverse Faraday effect. This effect occurs when circularly polarized light is incident on a nonabsorbing crystal, such as europium calcium fluoride, inducing a magnetic moment in the crystal.

The basic logic device includes polarizer 1, crystal 2 which exhibits the inverse Faraday effect, and coil 3 wound around the crystal. Operation of polarizer 1 occurs according to one of three methods. If it is a quarter-wave plate, it acts to change the plane polarized beam to a circular polarized beam. The state of circular polarization, left-hand or right-hand circularly polarized, depends on the relative orientation of the axes of the quarter-wave plate with respect to the direction of the incident beam. A change in the state of circular polarization is effected by mechanically orienting the quarter-wave plate.

Another method uses a birefringent crystal and a quarter-wave plate. In this method, the state of circular polarization is electrically controlled by applying a voltage across the birefringent crystal. The third method utilized provides for the application of a quarter-wave voltage to a birefringent crystal. If a monochromatic plane polarized beam is incident on the crystal. it is changed into a circularly polarized beam. The state of circular polarization changes according to the polarity of the quarter-wave voltage.

By arranging a number of such logic devices in a row, such as cells 5, 6 and 7, a word configuration of N bits is established. Laser source 8 provides a plane polarized laser beam 9 which can be modulated according to system requirements. Beam 9 has sufficient intensity to penetrate through all the cells of the word. Independent on the control exercised at 4 on polarizer 1, beam 9 remains linearly polarized, or is changed into one or the other state of circular polarization. The three possible states of polarization determine the storage state of crystal 2 as detected by coil 3. Thus, if the current through coil 3 is zero, one logical state is assumed. If the current flow is in one direction a second logic state is assumed and, if in the other direction, a third logic state is assumed. The informat...