Gallium arsenide waveguide interferometers and couplers for high-speed plectro-optic modulation and switching

The properties of electro-optic waveguide devices in GaAs, such as propagation and coupling loss, reflections, driving requirements, bandwidth, polarization sensitivity and on/off ratio, have to be optimized to allow their application as high-speed modulators in singlemode optical communication links. By using electron beam masks, lift-off and reactive ion etching techniques for the fabrication of rib waveguides in n-/n+ GaAs we have achieved device losses of less than 5 dB for both Mach-Zehnder interferometers and stepped Δβ directional couplers. Reflections from the coupling facets were reduced to less than.5% by SiO antireflection coatings. The driving voltages are between 10 V and 30 V and the modulation/switching bandwidths exceed 5 GHz. Results of system applications at data rates of more than 500 Mbit/s are reported.