Abstract

As technology improves, the spacing between magnetic disks and magnetic heads continues to decrease. However, the spacing must be accurately measured in order to maintain the reliability of magnetic disk systems. Typical spacing measurement methods are based on interferometry, in which a magnetic disk is usually replaced with a glass disk.¹ However we have developed a spacing sensor for measuring the space between the disk and a head. The operating principle of the sensor is based on Frustrated Total Reflection.² We optically integrated the sensor with the slider. However, before attaching the sensor to a real ceramic slider, we made a glass slider with a sensor on its side as shown in Fig. 1. The sensor structure is shown in Fig. 2. The sensor was fabricated on an SiO₂ wafer by making a V-shaped rib waveguide by spattering high index glass and covering the guide with SiO₂ for protection. The wafer was then cut and made into a glass slider. The light fed by a fiber was coupled to one arm of the waveguide with a small coupling prism. The light propagated along the arm of the waveguide, was reflected at the sensing area (top of the V pattern) and then propagated along the other arm of the waveguide. The reflected light was then decoupled from the waveguide by a small coupling prism and fed into the other fiber. The two fibers and two prisms were not connected to each other mechanically, therefore there was no force on the slider, that is, the behavior of the slider was not affected.

© 1994 Optical Society of America