Design, fabrication, and characterization of a two-dimensional photonic-crystal symmetric Mach-Zehnder interferometer for optical integrated circuits

We report on the design, fabrication, and optical characterization of a GaAs two-dimensional photonic-crystal-based symmetric Mach-Zehnder interferometer (PC-SMZ) aimed at all-optical switches in planar photonic integrated systems. The directional couplers that constitute the PC-SMZ interferometer prevent the occurrence of ring resonance which degrades the interference, and allow control pulses for the switching operation to be received. We show 50%- and 100%-power couplings from the transmission characteristics of the directional couplers, thus demonstrating their operation as 3-dB dividers in the PC-SMZ. We also show experimentally wavelength selectivity between signal and control pulses with a separation of ∼7nm. These results indicate that the structure is promising as an all-optical switch when a nonlinear material such as a quantum dot is introduced into both arms of the interferometer.