Butt-coupled waveguide-modulators by low temperature embedded CBE regrowth for high speed modulation (42 GHz) or large extinction ratio (>50 db)

The monolithic integration of optical waveguides with various active photonic devices is an essential step towards the fabrication of complex photonic integrated circuits (PICs). This integration requires on the same substrate side by side planar areas of usually thick (around 3 μm) InP/GaInAsP/InP double heterostructure (DH) with wide differences in bandgap and doping level between the low loss waveguide and the active device. We demonstrate that selective-area chemical beam epitaxy (SA-CBE) offers several interesting features for this application. We have successfully applied this technique to the selectively embedded regrowth of a waveguide butt-coupled to multi-quantum well (MQW) electroabsorption (EA) modulators. Two integrated modules have been fabricated and characterized: a photonic circuit including two modulators optically connected through a waveguide to generate short optical pulses with a large extinction ratio (>50 dB) for optical temporal multiplexing up to 80 Gb/s; and a very short (L=50 μm) discrete modulator with waveguides integrated on both ends showing high modulation bandwidth (42 GHz)