Precise Measurement of the Thickness of a Dielectric Layer on a Metal Surface by Use of a Modified Otto Optical Configuration

We propose a modified method for thickness measurement of a dielectric coating layer on metal based on Otto optical configuration (O-configuration). This method enables us to estimate the coating thickness that typically ranges from several tens of nanometers to more than one micrometer with precision less than a few nanometers. The common method to measure the thickness of dielectric coating layer is to utilize the frustrated total-internal reflection. In order to measure the thickness of several tens of nanometers, one can apply the surface-plasmon-resonance (SPR) phenomenon generated by the p-polarized light. For thickness larger than one hundred nanometers, a metal-clad leaky-waveguide (MCLW) mode generated by the p- or the s-polarized light can be employed without significant changes to the optical setup. The numerical and experimental verifications of the modified O-configuration reveals its effectiveness for precise measurement of moderately-thick dielectric coating layer on the metal.