One-Dimensional Photonic Crystals
Below is an SEM image of a air bridge structure fabricated (and imaged) by our colleagues K. Y. Lim, G. Petrich, and L. Kolodziejski in CMSE. This is a conventional waveguide, surrounded by air, into which a regular set of holes have been punched (the center to center spacing between the holes is 1.8 µm). The periodic structure provided by these holes creates a band gap, a one-dimensionally periodic photonic crystal (often referred to as simply a "one-dimensional" photonic crystal, although it exists in three dimensions). In the center of the bridge, a slight defect in the crystal has been formed by leaving extra space between the holes. This forms a resonant cavity which can be used as a filter. (This is a prototype design for 4.5 µm light; later designs have been scaled down for wavelengths of 1.5 µm.)
Be sure to note the small sculpture of a beaver thoughtfully included in the "river."