Optical Spectrum Analysis And Imaging Of Magnetic Tape Patterns Using The Kerr Effect

The power spectrum of a time varying signal may be realized using optical techniques by first converting the temporal variations to corresponding spatial patterns, then illuminating the spatial pattern with coherent, collimated light and observing the far field diffraction pattern. The light intensity distribution in the diffraction pattern is directly equivalent to the power distribution in the spectrum of the original signal (Ref.1). This paper describes the implementation and perform-ance of a real time, coherent optical spectrum analyzer that uses magnetic tape recording to convert temporal variations to corresponding spatial magnetic patterns, and uses the longitudinal Kerr magneto-optic effect to couple these magnetic patterns to a coherent illumination source. A magneto-optic transducer was developed that replicates the magnetic patterns from magnetic tape by contact printing and has magnetic and optical properties required to achieve a sufficiently large Kerr effect for practical applications.