Separation of photonic crystal modes using femtosecond time-of-flight in waveguides

Summary form only given. We use ultrabroadband ultrashort-pulse time-of-flight measurements to resolve how light propagates through silicon-nitride-based (SiN) photonic crystal and quasicrystal waveguides. Pulses from an amplified Ti:sapphire laser are used to generate a broadband supercontinuum which is focused into the 250 nm thick waveguides. After transmission through the photonic crystal region, the dispersed pulses are optically gated. By varying the time delay of this gating pulse, and collecting the time delayed spectra, a map of wavelength vs time delay can be built up with high spectral (1 nm) and temporal (150 fs) resolution.