Abstract
We present a simultaneous measurement of the route to chaos of the optical intensity and carrier density as the feedback strength is increased in an external cavity semiconductor laser (ECL). The intensity is measured with a high-speed photodetector while the carrier dynamics is obtained through a measurement of the dynamic voltage across the laser diode injection terminals. Both measurements demonstrate a route to chaos that stems from the undamping of the relaxation oscillation and provide confirmation of the predictions of the Lang and Kobayashi model concerning the routes to chaos.