Scanning heterodyne Kerr-effect microscope for imaging of magnetic tracks

Abstract

Design and performance of a new type of Kerr microscope based on heterodyne cross-polarized technique is presented. Weak depolarization of the probe beam due to longitudinal magneto-optical Kerr effect is detected by means of heterodyne mixing of the two cross-polarized and frequency shifted waves generated by Zeeman-type He–Ne laser. In comparison with the traditional homodyne method the proposed technique has better sensitivity and spatial resolution. Experimental results of imaging service magnetic tracks on real samples of magnetic disks are presented, showing better contrast and spatial resolution with respect to the images obtained from commercial devices available in the market.

Multi-Wave and Hybrid Imaging Techniques: A New Direction for Nondestructive Testing and Structural Health Monitoring

“…Kerr microscopy has always been considered as one of the most promising techniques for that purpose, due to the non-contact nature of the measurements. Vladimir V. Protopopov et al have applied a heterodyne cross-polarized technique for imaging service magnetic tracks on magnetic disks by means of the longitudinal Kerr effect in 2006 [ 105 ]. The advantages of this technique over both the homodyne and direct detection techniques include higher sensitivity and lower noise in the output signal.…”