Power and frequency modulation characteristics of a coupled cavity dynamic single mode GaAlAs laser

A commercially available GaAlAs diode laser has been modified to provide a stable dynamic single longitudinal mode laser. The laser was modulated with a power modulation index of more than 50 percent at microwave frequencies while operating in a single mode. Small signal modulation efficiency for optical power and frequency was measured together with the corresponding phase delays relative to the modulation current, in the frequency range 0.5 to 4 GHz. As predicted by the standard rate equation model, the laser frequency modulation index normalized to the power modulation index was a constant, independent of laser drive current and modulation frequency, and had a value of about 4. The phase advance of the frequency modulation relative to the power modulation was close to 90 deg over most of the frequency range, also in agreement with the rate equation model.