(a) Schematic and microscope image of nanocavity. (b) Calculated electromagnetic field distribution. (c) Experimental resonant spectrum.
Ultrahigh-Q Photonic Crystal Nanocavity Realized with Locally Modulated Line Defect
It is known that a gpoint defecth in a photonic crystal acts as an optical cavity and a gline defecth acts as an optical waveguide. We found that a local weak width modulation of a line defect can form an ultrasmall, ultrahigh-Q nanocavity. In the Si photonic crystal nanocavity sample shown in the above figures, some of the holes surrounding the line defect are shifted away by several nanometers (too small to see in the figures) to create the cavity. The nanocavity has overcome the experimental one million Q barrier for the first time. This was believed to be impossible to achieve with photonic crystal cavities only a few years ago. (Page 48)