  The demonstration of an optical fiber based probe for efficiently exciting
the waveguide modes of high-index contrast planar photonic crystal (PC) slabs
is presented. Utilizing the dispersion of the PC, fiber taper waveguides formed
from standard silica single-mode optical fibers are used to evanescently couple
light into the guided modes of a patterned silicon membrane. A coupling
efficiency of approximately 95% is obtained between the fiber taper and a PC
waveguide mode suitably designed for integration with a previously studied
ultra-small mode volume high-Q PC resonant cavity [1]. The micron-scale lateral
extent and dispersion of the fiber taper is also used as a near-field spatial
and spectral probe to study the profile and dispersion of PC waveguide modes.
The mode selectivity of this wafer-scale probing technique, together with its
high efficiency, suggests that it will be useful in future quantum and
non-linear optics experiments employing planar PCs.
