Ultrahigh-Q nanocavities fabricated by scanning probe microscope lithography on pre-patterned photonic crystal

The details of cavity formation mechanism are described in this paper. The pre-patterned structure is a line defect waveguide in a two-dimensional (2D) photonic crystal slab, and we assume that the refractive index is modulated in the yellow shaded region. A very small spatial index modulation (Δn/n <; 0.1%) changes the mode-gap edge frequency of the modified area to create barrier regions, while the unmodified area retains its original mode-gap edge frequency. As a result, an ultrahigh-Q cavity with a small volume can be created.