Demonstration of high-brightness-mode propagation in a compound waveguide structure

We demonstrate the existence of an unusual and useful high-brightness guide d mode of a multimode AlGaAs/GaAs heterostructure compound slab waveguide. This mode has a narrow near-field single lobe confined to the low-index reg ions of the waveguide. This mode was selectively probed by optically exciti ng quantum wells optimally placed in the waveguide. By pumping in a stripe geometry, lasing is observed above a threshold of 80 kW/cm(2) indicating ef ficient lasing in the highest-order waveguide mode. The near-field emission pattern of the waveguide was imaged to provide a direct measurement of the intensity profile of the higher-order mode. (C) 1999 American Institute of Physics. [S0003-6951(99)02128-2].