Polarization interferometer for measuring the flying height of magnetic read-write heads

Traditional optical flying-height testers use only the normal-incidence reflectivity of the interface between the read-write slider and a glass disk surrogate. We propose a tester that fully analyzes the complex amplitude ref lectivity of the interface, including the polarization-dependent complex phase. The new approach is more accurate and repeatable and has no loss of precision at zero flying height. Further, the same instrument directly measures the complex index of refraction for the slider material in situ, obviating the need for a separate metrology step with an ellipsometer.