Dark spatial solitons in semiconductor microcavities

This study reports the characteristics of dark solitons different from bright solitons. A striking feature of dark solitons observed in this work is a reflectivity higher than 1 at the center of the soliton. The reflectivity higher than 1 results because the soliton collects energy from its surrounding. As has been predicted for bright solitons this constitutes an optical amplification mechanism worthwhile considering for technical applications. Results show that in addition to the differential gain predicted for bright solitons, the dark solitons experimentally observed permit "DC gain", i.e. the reflected intensity is higher than the incident intensity. Thus dark solitons show "absolute" gain.