Dispersion properties of silicon nanophotonic waveguides investigated with Fourier optics

We experimentally investigate the dispersion relation of silicon-on-insulator waveguides in the 1.5 microm wavelength range by using a technique based on far-field Fourier-space imaging. The phase information of the propagating modes is transferred into the far field either by linear probe gratings positioned 1 microm away from the waveguide core or by residual gratings located on the sidewalls of the waveguide. As a result, the dispersion curve of rectangular and slot waveguides as well as the group index dispersion are accurately determined.