Near-field analysis of metallic DFB lasers at telecom wavelengths

We image in near-field the transverse modes of semiconductor distributed feedback (DFB) lasers operating at lambda approximate to 1.3 mu m and employing metallic gratings. The active region is based on tensile-strained InGaAlAs quantum wells emitting transverse magnetic polarized light and is coupled via an extremely thin cladding to a nano-patterned gold grating integrated on the device surface. Single mode emission is achieved, which tunes with the grating periodicity. The near-field measurements confirm laser operation on the fundamental transverse mode. Furthermore - together with a laser threshold reduction observed in the DFB lasers - it suggests that the patterning of the top metal contact can be a strategy to reduce the high plasmonic losses in this kind of systems. (C) 2013 Optical Society of America