Miniature integrated optical beam-splitter in AlGaAs/GaAs ridge waveguides

Typical directional couplers in semiconductor waveguides require long (several millimetre) interaction lengths, potentially limiting their use in future optoelectronic integrated circuits (OEICs). We report the fabrication and operation of a newly designed integratable waveguide beam-splitter device only micrometres in size, consisting of a groove at the intersection of two perpendicular AlGaAs/GaAs ridge waveguides which was milled with a microfocused gallium ion beam. Single-mode propagation of both transmitted and reflected beams was observed, and the power ratio between both beams was adjustable by varying the groove depth.