Analysis of Dispersion Characteristics of Planar Waveguides via Multi-Order Interrogation of Integrated Bragg Gratings

We demonstrate experimentally a simple technique to measure the wavelength-dependent effective refractive index of a waveguide utilizing integrated Bragg grating structures. A broadband measurement of the Bragg wavelengths yields the effective index of the waveguide and, thus, an accurate total dispersion relationship. An empirical calculation of the waveguide component of the dispersion yields both the waveguide and material dispersion components of the measured total dispersion. The technique allows direct measurement of the effective index of the waveguide and yields a zero dispersion wavelength at 1220.5 nm in our silica-on-silicon platform. Importantly, inclusion of second-order Bragg reflections improves the accuracy of modal refractive index for near-visible wavelengths.