Characterisation of Photonic Crystal and Nanophotonics Devices with Fourier Optics

We report on the experimental investigation of the Floquet-Bloch modes propagation inside photonic crystal (PhC) structures as well as their emission from the structures with far-field optics. We demonstrate that far-field optical experiments can be used to retrieve fundamental optical properties of PhC structures, such as the light path, the dispersion curves above and below the light cone, and the equi-frequency surfaces both in one and two dimensions, in a single step and without numerical post-processing. The combination of an end-fire set-up working in the 1.5 mum range, generally used to measure the transmission through the waveguide, along with a high numerical aperture Fourier space imaging set-up, allows a fine spectral analysis of each mode of the photonic structure. In particular, this allows to accurately measure dispersion curve of coupled cavity waveguides and of single line defect PhC waveguide specially designed to operate in the slow light regime below the light cone. Measurement of the full complex-valued allows to determine the impact of the disorder on the light transport, a key issue in slow light application of PhC.