Surface Mode Coupling in GaAs/AlGaAs Laser Diodes - A New Technique for a Single Mode Laser

We present a novel technique for the realization of a single mode laser diode. The concept is based on a coupling process between the laser mode propagating in the active region and a surface mode on top of the laser diode. This technique provides both efficient surface emission with a low beam divergence as well as a single-mode-like emission from a conventional GaAs/AlGaAs double heterostructure laser diode. The emission spectra are explained by a model based on ray optics, which allows an optimization of this technique. The main advantage of this new type of laser diode is its simple fabrication, which requires no regrowth like is the case for single mode DFB laser diodes.