| Perhaps the largest
obstacle in preventing the widespread use of planar photonic crystal
devices is the inability to efficiently couple light into them.
The main reason for this lies in the enormous mode mismatch between
an incident field and that of a PhC channel waveguide. As a result,
when direct coupling is attempted, the small mode overlap results
in low efficiency coupling. Currently, among the experimental coupling
methods reported in the literature, coupling losses range from ~20-30
dB, or in other words, typically only one percent of the optical
power ends up in the photonic crystal channel. Such loss is unacceptable
if photonic crystal devices are to be of practical use in next generation
opto-electronic systems. |
