Design of ultrahigh-Q photoinduced cavities in defect-free photonic crystal slabs.

We demonstrate numerically that a cavity can be induced in a defect-free photonic crystal slab made of photosensitive material such as chalcogenide glass. A key advantage of the design is the possibility for complete post-processing in an otherwise defect-free structure, and the cavity can thus be formed anywhere in the photonic crystal. We demonstrate that high-Q cavities with Q~10(8) can be designed in this way. Since the high-Q mode can originate from an air-band, these cavities appear to be ideal candidates for sensing applications.