Photonic crystals have many potential applications because of their ability to control light-wave propagation. We report on the fabrication and properties of quasi-two-dimensional photonic crystals with triangular lattices of dielectric rods in air. Rod-type photonic crystal structures were fabricated in silicon by electron beam lithography and dry-etching techniques. Mach–Zehnder interferometers were fabricated from two-dimensional photonic crystal waveguides. Transmission spectra were measured and device operation was shown to be in agreement with theoretical calculations. The interferometers can be used in the visible light region. Such an approach to photonic element systems should enable new applications for designing components in photonic integrated circuits. Physica E: Low-dimensional Systems and Nanostructures 40(8), pp.2800-2804