Bode plots applied to microscopic interferometry

Abstract

We describe a technique for using Bode plots in microscopic interferometry, in particular as applied to the three Gaussian beam interferometer recently reported in the literature. The technique is used in a similar manner to its application to an electric or electronic system in finding its frequency response. The Bode response is used to deconvolve the raw data obtained directly from the interferometer to compensate for the data in frequency, making it possible to obtain more realistic profiles of the samples under test. We apply this technique to obtain profiles of the inner reflective layers of two optical types of surfaces for data storage commercially available, namely, the compact disk (CD-R) and the digital versatile disk (DVD-R). We report the experimental results of radial scans of these devices without data marks, before and after applying the transfer function of the system. The measurements are obtained by placing the devices with the polycarbonate surfaces so as to aim the probe beam of the interferometer at them, taking advantage of the vertical depth discrimination of the microscope. We show that the resulting profiles, obtained across the Polycarbonate layer, measured with this interferometer, give valuable information of the real track profiles, making the combination of the Bode plots with this interferometer a suitable tool for quality control of the surface storage devices.