A New Method of Measuring Localized Chromatic Dispersion of Structured Nanowaveguide Devices Using White-Light Interferometry

We report on a simple and direct method of measuring localized chromatic dispersion (CD) profiles of structured nanowaveguide devices using white-light interferometry. Phase change in the interference fringe of a white-light interferometer (WLI) caused by introducing a sample-under-test into one of the interferometer arms was used to determine a spectral profile of its accurate CD coefficients. This method was tested by measuring the spectral CD profiles of a localized silicon nanowaveguide and of a nonmembrane-type photonic crystal waveguide (PhCW) excluding their optical coupling sections. The measured local CD values of a 500-nm-wide single-line-defect (W1) PhCW with a lattice period of 460 nm and the hole radius of 165 nm formed on 220-nm-thick silicon layer of a silicon-on-insulator (SOI) wafer varied from 0.38 to 0.22 ps/(nm ·cm) for a wavelength range from 1530 to 1570 nm. This method will be very useful in determining the accurate CD profiles of nanophotonic waveguide devices.