Monolithically integrated transverse-junction-stripe laser with an external waveguide in GaAs/AlGaAs

Abstract

This device consists of a five-layer transverse-junction-stripe laser structure monolithically integrated with an external three-layer waveguide. The transverse p-n junction within the laser cavity permits the use of a vertical p-n junction in the external waveguide for future implementation of a modulator without disturbing the laser operation. As a result, this structure allows for flexibility in the design of the external waveguide/modulator without resorting to complicated regrowth procedures. Design curves for two different types of optical cavities are presented, and the reflectivity and transmission of the etched facet as a function of active layer thickness is modeled in detail using an excitation field approach. Finally, integrated laser/waveguide devices are fabricated based on this design and are compared to the theoretical curves. Most devices had threshold currents between 60 and 80 mA, while laser-to-waveguide transmission coefficients were as high as 38%.