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Optically Written Vortex Memory

IP.com Disclosure Number: IPCOM000050570D
Original Publication Date: 1982-Nov-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 3 page(s) / 53K

Publishing Venue

IBM

Related People

Faris, S: AUTHOR [+2]

Abstract

Vortex memories are known in which quantized fluxoids represent information and can be moved in a superconducting layer. In the present scheme, these fluxoids are moved between two potential wells which are separated by weak links. Depending upon the position of the vortex, it represents either a binary one or a binary zero. An optical beam incident on the weak link will lower its potential barrier so that the vortex can be moved from one potential well to the other. This device is suitable for two-dimensional Fourier transforms of functions and their inverses, and also for enhancing image quality by spatial filtering of a known noise background.

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Optically Written Vortex Memory

Vortex memories are known in which quantized fluxoids represent information and can be moved in a superconducting layer. In the present scheme, these fluxoids are moved between two potential wells which are separated by weak links. Depending upon the position of the vortex, it represents either a binary one or a binary zero. An optical beam incident on the weak link will lower its potential barrier so that the vortex can be moved from one potential well to the other. This device is suitable for two-dimensional Fourier transforms of functions and their inverses, and also for enhancing image quality by spatial filtering of a known noise background.

Fig. 1A shows a side view of the experimental arrangement and illustrates how a binary one is written by moving a vortex from left to right, while Fig. 1B is a side view of the arrangement illustrating how to write a binary zero by moving a vortex from right to left. A plot of the potential barrier U(X) of a weak link as a function of the distance X measured between two potential wells is also a part of Fig. 1A. Fig. 2 is a top view of the arrangement. OPTICAL WRITING:

Figs. 1A and 1B show side views of a ground plane 10 which contains potential wells W(L) and W(R) and superconducting weak links 12 through which current I(GT) flows. A control line 14 above the ground plans carries transport current I(T). A memory cell consists of two potential wells, a left well (W(L) and a right well (W(R)). The cell is defined to be in the "0" state if W(L) contains a quantized vortex, while W(R) contains no vortex. The transport current I(T) flowing in the meandering control line 14 (Fig. 2) sets up the whole memory array to be in the "0" state, i.e., all W(R)'s of the array contain no vortices while all W(L)'s do. Write "1":

The groundplane current I(GT) (Fig. 1A) is caused to flow through all the weak links. If I(CIR) is the circulating current generated by the vortex stored in the well W(L), I(GT) is such that I(CIR) + I(GT) is less than the Josephson critical current I(0) of the weak links. The Lorentz force which tends to move the vortex is not enough to surmount the potential barrier 16 (Fig. 1A). An optical beam guided by a fiber 18 is switched on and irradiates only the weak link region. The absorbed optical photons cause I(0) to diminish. Thus, the potential barrier is reduced (dashed curve 20) and the Lorentz force moves the vortex from W(L) to W (R). The optical beam and then I(GT) are turned off, a sequence which guarantees that the vortex remains stable in W(R). A "1" is now written in the cell. Write "0".

By changing the polarity of I(GT), the Lorentz force acts in the opposite direction and tends to move the vortex from W(R) to W(L) (Fig. 1B.). Once again ...