We explore experimentally a new regime of operation for modelocking in a Ti:Sapphire laser, where the threshold for mode locking is lower than the threshold for continuous-wave operation.

A well known feature of mode locking (ML) is that the transition between continuous-wave (CW) and ML operation in terms of pump power is abrupt. Only when the pump power crosses a certain threshold, ML can be initiated by creating noise in the cavity as a seed to start the pulsation process. Another characteristic feature of ML is that the threshold pump power for ML is higher than the CW threshold. It seems as if a certain amount of CW oscillations in the cavity is necessary, and only on top of an existing CW can the small noise seed be amplified to create the pulse. Yet, the question whether the preliminary existence of a CW oscillation is a necessary condition for ML operation was not directly explored. In this work, by further enhancement of both the nonlinearity and the losses for the CW operation we show that: 1. the intra-cavity CW power needed to initiate ML can be reduced down to zero, 2. ML can be sustained with pump power even below the CW threshold, and even though a CW solution does not exist in this regime, a stable pulse oscillation can be realized. The "sweet spot", where the thresholds for pulsed and CW operations meet, offers high performance for mode locking with low threshold pump power and very low intra-cavity average power.