Methods for improving the signal-to-noise ratio of photon and electron beam accessed magnetic-film memory systems

Methods are described for reducing shot noise in magnetic-film memories which are to be read magnetooptically with the auxiliary aid of an electron beam. In such memories the principal source of shot noise is from the light which is used to illuminate the memory array. The following methods of reducing array shot noise are considered: 1) selective background, 2) magnetooptical balance, 3) temperature control of magnetooptical spectra in rare-earth iron garnets (REIG). It is concluded that the use of REIG spectra appears to offer not only the best but also a satisfactory solution to the array shot-noise problem.