The Q-Switching Instability of Passively Modelocked Solid-State Lasers

Passively modelocked lasers often exhibit an instability at low pumping levels, characterized by periodic variations in pulse energy across successive cavity roundtrips (see Fig. 1). This phenomenon, called Q-switched modelocking (QML), shares its origin with passive Q-switching in singlemode solid-state lasers employing saturable absorbers. Increasing the pump power suppresses QML, allowing regular modelocked pulses (or cw pulses) to stabilize.