Suppression of the relaxation oscillation in the modulated output of semiconductor lasers

Practical rates of direct pulse modulation of semiconductor lasers have so far been limited to below several hundred megahertz, owing to serious distortion in the output signal caused by the relaxation oscillation of the light intensity. Based on theoretical analysis of the dynamic properties of lasing under constant injection of external radiation into the cavity modes, light injection is proposed as a method for suppressing the relaxation oscillation. The effectiveness of this method has been confirmed in a series of preliminary experiments which employed GaAs injection lasers both as the modulated laser and as the external source of the injected radiation.