New Methods of Magneto-optical Signal Modulation and Detection

Abstract

Methods of modulating magneto-optical signals are useful in improving the signal-to-noise ratio of practical systems. Using the longitudinal or polar magneto-optical orientation and incident light polarized out of the plane of incidence (say at 45°), an intensity-modulated magneto-optical signal can be generated by modulating the phase of the component of light which is ‖ (or ⊥) to the plane of incidence. No analyzer is required with the consequence that this type of modulation can be used in fully focused light if axial symmetry is maintained. Signal modulation can also be obtained by thermal modulation of the magnetic material. For a 1-μ-diam region of a thin film the frequency response is calculated to be ∼500 MHz. Various magneto-optical configurations are readily devised which yield the value of a bit (1 or 0) in terms of the phase (0 or π) between the magneto-optical signal and the electron-beam intensity modulation. If the thermal modulation is effected by an electron beam, the need for a high-resolution optical deflector is eliminated in a high-bit-density computer-memory application.