70-GHz relaxation oscillation in a vertical cavity surface emitting laser

Very-high-frequency relaxation oscillations were measured in an electrically pumped vertical cavity surface emitting laser (VCSEL). The measurements were performed over a range of drive currents, and a 71-GHz relaxation oscillation was observed when current injection was maximum. The lasers used for the measurements consisted of an active region of 3 In/sub 0.2/Ga/sub 0.8/As quantum wells. CW (continuous-wave) measurements showed a very high resonance frequency-square root of power coefficient of 7 GHz/ square root mW. The maximum resonance frequency was limited to 7 GHz by heating. The larger signal pulse responses also showed a linear dependence of relaxation oscillation frequency on square root of current above threshold, with a maximum of 71 GHz for a peak drive voltage on the order of 15 V.