Abstract
The aim of this work is to investigate coupling techniques and structures to
minimize the coupling losses between dielectric waveguides and planar photonic
crystals circuits. The modeling of the coupling between dielectric and photonic
crystal waveguides has been carried out. Closed form expressions for the reflection
and transmission matrices that completely characterize the scattering that occurs at
the interface between dielectric and photonic crystal waveguides have been
derived. The influence of the main parameters of the photonic crystal on the
coupling efficiency has also been analyzed. To improve the coupling efficiency
from both narrow and broad dielectric waveguides, a novel coupling technique
based on setting a number of localized defects within a discrete photonic crystal
taper has been proposed. Different approaches, including genetic algorithms, have
been reported to design the optimum configuration of defects. Once efficient
coupling from dielectric waveguides into photonic crystal waveguides has been
achieved, efficient coupling into coupled-cavity waveguides has been pursued. An
adiabatic coupling technique based on progressively varying the radii of the
spacing defects between cavities has been proposed. Furthermore, a rigorous
analysis of pulse propagation in frequency and time domains has been carried out
for characterizing the influence of the coupling efficiency on the main parameters
of the pulse. Finally, the fabrication and experimental demonstration of the
proposed coupling techniques have been addressed.