High-Q microfluidic cavities in silicon-based two-dimensional photonic crystal structures.

We demonstrate postprocessed microfluidic double-heterostructure cavities in silicon-based photonic crystal slab waveguides. The cavity structure is realized by selective fluid infiltration of air holes using a glass microtip, resulting in a local change of the average refractive index of the photonic crystal. The microcavities are probed by evanescent coupling from a silica nanowire. An intrinsic quality factor of 57,000 has been derived from our measurements, representing what we believe to be the largest value observed in microfluidic photonic crystal cavities to date.