Spectrally resolved complex transmittance measurements of infrared nanostructured devices

Abstract

Optical sub-wavelength structures allow to code space-varying complex transmittance functions that induce both amplitude and phase variations on a given wavefront at the micrometer scale. This paves the way to the miniaturization of optical devices based on the spatial coding of the complex transmittance. We describe here a dedicated setup in the infrared range (3-14µm) for the spatial and spectral characterization of such components. The setup combines (i) a quadri-wave lateral shearing interferometer, which enables a two dimensional measurements of phase and amplitude, and (ii) a Fourier Transform Infrared Interferometer for spectral resolution. We present both theoretical simulations and experimental results of the characterization of sub-wavelength gratings.