Mach-Zehnder channel-guide device structure based on 2D photonic crystal

We have fabricated and measured 2D photonic crystal Mach-Zehnder device structures using W1 channel waveguides oriented along GK directions in AlGaAs/GaAs epitaxial waveguide material and silicon-on-insulator waveguide material, with operation at wavelengths around 1550 nm. 2D FDTD simulations and experimental results will be shown and compared. The structure has been designed using progressive tapering of the hole diameter in the bend regions, while a 'defect' hole with reduced radius has been placed in the centre of the Y-Junction, giving a substantial improvement in the transmission and bandwidth. The overall length of the photonic crystal Mach-Zehnder structure is typically about 32 µm and the structure has been fabricated using a combination of direct-write electron-beam lithography (EBL) and dry-etch processing. Devices were measured using a tunable laser with end-fire coupling. We shall describe the application of such structures for switching and sensing, with deliberate exploitation of the thermo-optic effect via the incorporation of heater electrodes