Near-field optical microscopy of thin photonic crystal films

Near-field optical microscopy is used to image the light propagating in a S i3N4-on-silica film with a strip of deeply etched submicron holes in the ce nter. Fringe patterns created by interference between incident and diffract ed guided modes are observed in the smooth waveguide surrounding the large air-hole photonic film. Observation of the fields in the photonic crystal r egions indicates that out-of-plane scattering at the smooth/periodic transi tions and leakage caused by grating coupling play major roles. The effects of different air-hole sizes and lattice pitches are also explored. (C) 1999 American Institute of Physics. [S0021-8979(99)01809-5].