Observing Extremely Dispersive Light in Photonic Crystals and Cavities

We discovered a small mistake in the dataprocessing. Please see or our next output for the corrected version.

Developed an interferometric optical reflectivity microscope to observe phase-sensitive reflectivity of nanophotonic structures. High spatial and spectral resolution over broad frequency ranges (750 < λ < 2500 nm). From frequency-resolved phases obtain the (group) time delay. Study planar microcavities (GaAs/AlAs), and Silicon three-dimensional (3D) photonic band gap crystals. For planar microcavity with stopband centred at 1331 nm and a Δω/ω≈16%, we observe time delays τ_g> 4 ps for L = 4.66 μm thickness. For 3D woodpile crystal observe time delays τ_g> 550 fs for L = 780 nm thickness. Combined with the very thin metasurface structure, this yields a lower bound for the group index of n_g≥ 100, much more than previously observed in photonic crystal waveguides.