Experimental investigation on a Q-switched, mode-locked fiber laser based on the combination of active mode locking and passive Q switching

We performed an experimental investigation on a Q-switched, mode-locked laser based on the combination of passive Q switching and active mode locking. This study was carried out using an erbium fiber ring laser incorporating an active mode locker employing a fast Si-based variable optical attenuator and a passive Q switch based on a carbon nanotube saturable absorber. It was found that stable Q-switched, mode-locked pulses can be readily generated when using a particular cavity modulation index and pump power. It was also found that our scheme can easily alter the operating regime among the Q switching, Q-switched mode locking, and mode locking by simply controlling the cavity modulation index and/or the pump power. For this particular laser configuration, the cavity modulation index and pump power operating conditions have been experimentally analyzed for three laser operating regimes.