1.55-μm InGaAsP-InP laser arrays with integrated-mode expanders fabricated using a single epitaxial growth

We report on two techniques for the realization of expanded-mode laser arrays with a single epitaxial growth step and conventional fabrication techniques. Laser arrays with integrated adiabatic-mode expanders (AME) based on a tapered active region and an underlying passive coupling waveguide are demonstrated at the 1.55-μm wavelength. These lasers butt couple to standard cleaved single-mode fibers (SMF´s) with a loss of only 3.6 dB. This coupling efficiency compares with a theoretical calculation of 3.2 dB. We also propose a novel realization of a laser with an integrated-mode expander based on resonant coupling between a tapered active waveguide and an underlying coupling waveguide. Three-dimensional (3-D) beam propagation method (BPM) results are presented which show that compact, efficient mode expanders with a mode transformation loss of only 0.36 dB can be realized using this method. Butt-coupling efficiencies of 2.6 dB are possible to standard cleaved single-mode fibers