Experiments on linewidth reduction by fast electrical feedback

We report our first results on broadband electrical feedback applied to tunable lead-salt diode lasers. We use a heterodyne technique in combination with electronic frequency discrimination to reduce the diode-laser linewidth. The loop band width is about 10 MHz. We present results on high-frequency modulation to study the frequency response of the diode laser. From this experiment we are able to estimate the carrier tuning rate of the used lead-salt diode laser. Preliminary results in linewidth reduction by fast electrical feedback promise the possibility to apply the fast electrical feedback technique to lead-salt diode lasers.