D. O'Brien

Dependence of extrinsic loss on group velocity in photonic crystal waveguides.

We examine the effects of disorder on propagation loss as a function of group velocity for W1 photonic crystal (PhC) waveguides. Disorder is deliberately and controllably introduced into the photonic crystal by pseudo-randomly displacing the holes of the photonic lattice. This allows us to clearly distinguish two types of loss. Away from the band-edge and for moderately slow light (group velocity c/20-c/30) loss scales sub-linearly with group velocity, whereas near the band-edge, reflection loss increases dramatically due to the random and local shift of the band-edge. The optical analysis also shows that the random fabrication errors of our structures, made on a standard e-beam lithography system, are below 1 nm root mean square.

Coupled resonant modes of dual L3-defect planar photonic crystal cavities

We present the realization of 2-D photonic crystal cavities with a dual L3-defect geometry. The experimental results show consistent and predictable splitting of the fundamental modes and reveal clear evidence for strong cavity-cavity coupling.

Cavity-enhanced polarization control and observation of off-resonant coupling in quantum dot nanocavities

We study the linear polarization of the emission from single quantum dots (QDs) embedded in an “L3” defect nanocavity in a two-dimensional photonic crystal. We found that all the dots we observed emitted very strongly linearly polarized light. In stark contrast to the behaviour observed in QDs emitting into a homogeneous medium, the QD polarization has the same orientation as the spectrally closest photonic mode. Surprisingly, this is true even in the cases where the QDs are detuned by several times the mode linewidth, where the off-resonant Purcell enhancement should be 10−3 times that on resonance.