Direct modulation of lasers by dispersive threshold switching

For switching on and off semiconductor lasers usually the gain in the active medium is varied by modulating the injection current. A second possibility is to integrate an absorber section and to modulate the additional losses. In both cases the net gain is varied. Topic of this paper is to demonstrate for the first time an alternative modulation technique, where the laser can be operated at a fixed net gain. The switching is achieved by modulating electrically the threshold of the laser. Potential advantages are reduced switching power, higher switching speed, and minimized chirp.