Integrated laser-waveguide structures using selective area intermixing

Photonic integrated circuits such as integrated laser-modulators require side by side planar areas with differential bandgap. Structures grown in single step epitaxy permit very efficient coupling between the different regions of the device. This has been demonstrated by selective area growth (SAG) using metalorganic vapor phase epitaxy for laser-modulator applications at 1.55 μm. On the other hand, selective area intermixing (SAI) appears as a promising technique to control the differential wavelength between two regions. Such a technique provides maximum coupling efficiency (100%) between two sections of different band gap and leads to a reduction of the number of growth steps. In this paper, we report on the optical and electrical properties of InGaAsP/InP compressive strained multiple quantum well (MQW) laser-guide structures obtained by SAI under phosphorus over pressure in a vacuum sealed quartz ampoule. In this technique, the linear time dependence of the photoluminescence (PL) blue shift due to group V elements interdiffusion allow us to control the differential wavelength between dielectric capped and uncapped areas. The interdiffusion is strongly reduced in the dielectric capped areas and results in a low PL blue shift. Low threshold current densities are obtained in both areas even for a PL blue shift as large as 170 nm. In addition, optical intensity modulators based on the quantum confined stark effect (QCSE) exhibit high extinction ratio of -30 dB (λ=1.55 μm) with reverse driving voltage of about 1.2 V