Monolithic integration of GaAs-AlGaAs quantum-well lasers with directional couplers using vertical coupling of light

A novel technique for the monolithic integration of a laser and a directional coupler in the GaAs-AlGaAs material system is demonstrated. The combination of single-step molecular beam epitaxy (MBE) on a planar substrate, vertical coupling of light between the active and passive waveguide in a p-n-p-doped structure and the use of a self-aligned fabrication process for the ridge waveguides in the active and passive sections results in a threshold current of 52 mA and an output power of up to 0.6 mW. The directional coupler is completely switched at an applied bias of 4.0 V.