Metrology of holes in gold nano-film using interferometric microscopy

We present an optical metrology technique based on phase-shifting interferometric (PSI) microscopy applied to circular holes in a gold nano-film. We demonstrate that the optical phase measured at the image plane can be accurately calculated, even in the presence of diffraction. For holes with a radius less than 200 nm, the optical phase exhibited a strong dependence on hole size, highlighting the metrological potential of this technique. Measurement of the coherent impulse response of the interferometric microscope, and refractive index measurements of nanoparticles and nano structure s are also discussed as potential applications.