A Magneto-optic Polarization Readout Model

Abstract

Information stored on magneto-optic disks is typically read using a linearly polarized laser beam whose state of polarization is altered by the Faraday and/or polar Kerr effects upon reflection from the recording medium. Polarization sensitive optics are used to convert these media induced polarization changes into irradiance variations at photodetectors. Because the magneto-optic polarization effects are small (typically less than one degree of polarization rotation in the reflected beam) it is essential that the optical system introduce little additional polarization change if the recorded signal is to be recovered faithfully. This paper describes a polarization model that is used to predict the effects that real optical elements will have on the readout signals, noise, and ultimately, the signal to noise ratio of a magneto-optic recording system.