Optimisation and regime characterisation of monolithic semiconductor mode-locked lasers and colliding-pulse mode-locked lasers at microwave and millimetre-wave frequencies

The optimisation of the saturable absorber section length for mode-locked ridge waveguide lasers in GaAs/AlGaAs double quantum-well material is reported. Mode-locked lasers and colliding-pulse mode-locked lasers were fabricated using a simple self-alignment process. Regime analysis and signal characterisation are performed as a function of the laser cavity and saturable absorber section lengths. Device degradation is evaluated and compared in both configurations. Device performance in the frequency domain is assessed using both an external fast photodiode and the saturable absorber section, and the direct generation of millimetre-wave signal through the saturable section is discussed.