Fast-Light to Slow-Light Switching in a Laser Cavity

We report on experimental work investigating slow- and fast-light in a ring-laser cavity that utilizes a semiconductor optical amplifier (SOA) as its primary gain medium. By allowing a pulse to propagate around the loop multiple times, we are able to achieve a tunable delay-bandwidth product near 10 for a 10-ps pulse. Our results show a shift between fast-light, as expected in a typical SOA, to slow-light as the pulse propagates around the loop. This slow-light phenomenon in a gain medium is not expected from an SOA, but arises due to the interaction between the lasing mode and the signal mode.