Identification of localized group-velocity dispersion of nanostructured silicon waveguide devices using white-light interferometry

Abstract

This paper presents our recent achievement with a simple white-light Mach-Zehnder (MZ) interferometric method to identify localized group velocity dispersion (GVD) coefficient or group delay dispersion (GDD) value of the nanostructured silicon waveguide devices (NSWDs). Conventional methods of measuring the GVD of optical fibers or waveguides are related to measurement of the total GVD of the entire fibers or NSWDs. Recently time-resolved heterodyne detection technique and the near-field scanning microscopy technique are demonstrated to measure localized group delay of the photonic crystal waveguides (PhCWs) devices, but the techniques have a limited group delay (GD) resolution depending on laser pulse-width used for the measurement. It is demonstrated that our white-light interferometric method can measure very accurate GDD value up to 0.5 fs/nm resolution. This method has been applied to determine not only the GVD or GDD profile of the entire NSWDs but also that of their localized structural sections, such as grating couplers and interface between the plain strip waveguide and single line-defect (W1) PhCW.