LINEWIDTH, TUNABILITY, AND VHF-MILLIMETER WAVE FREQUENCY-SYNTHESIS OF VERTICAL-CAVITY GAAS QUANTUM-WELL SURFACE-EMITTING LASER DIODE-ARRAYS

We report the measurement of the laser linewidth, wavelength tunability, and the generation of microwave frequencies between individually addressable elements of a vertical-cavity GaAs quantum-well surface-emitting laser diode array (lasing in the wavelength range 850-865 nm). Using heterodyne techniques, we obtain a deconvolved 65 MHz laser linewidth from the 109 MHz beat signal. The laser linewidth corresponds to a semiconductor laser linewidth enhancement factor alpha = 5.7 which is in excellent agreement to that obtained independently from optical gain measurements and corresponding calculated refractive index changes. We measured heterodyne beat frequencies of 2-20 GHz. (The bandwidth was limited by our microwave amplifiers.) A simple calculation shows that a tuning range of 65 MHz-to-3 THz can be achieved.