Scanning near-field optical studies of photonic devices

The results presented here show that SNOM has a vital role to play when it comes to charac- terizing photonic crystal devices. The light inside a photonic crystal is modulated at the sub- wavelength scale and SNOM is the only technique that can actually image these behaviours. The key advantage of being able to resolve such fine detail, is being able to compare ex- perimental results with numerical models directly. Another important feature is the ability to measure from the surface of the crystal, thereby allowing measurement of point-to-point loss. We believe, furthermore, that SNOM is sensitive enough to demonstrate optical effects due to the tiny, but inevitable, imperfections in device fabrication. Direct measurement of these effects will allow refinement and optimization of device design. Finally, experiments carried out so far on silica microspheres and ridge waveguide structures, point the way for future applications to photonic crystal structures involving phase sensitive measurements and combinations of spectroscopy and microscopy.