Experimental demonstration of photonic crystal directional coupler at microwave frequencies

The performance of a directional coupler based on photonic crystal waveguides is theoretically studied and experimentally verified at microwave frequencies. Simulation results using a time domain method confirm the theoretical analysis and show a good agreement with the measurements. It is shown that coupling lengths as short as 3.5λ can be attained from this approach. Photonic crystal directional couplers are envisaged as a key building-block in ultra-compact photonic integrated circuits such as optical modulators, wavelength demultiplexers or optical switches based on photonic crystal technology.