Generation of high repetition rate femtosecond pulses from a CW laser by a time-lens loop.

We demonstrate a novel method for femtosecond pulse generation based on a time-lens loop. Time division multiplexing in the loop is performed so that a high repetition rate can be achieved. Pulse width less than 500 fs is generated from a continuous wave (CW) laser without mode locking, and tunable repetition rate from 23 MHz to 400 MHz is demonstrated. Theoretical analysis shows that the repetition rate is ultimately limited by the in-loop interference. By using a 2 x 2 optical switch, such interference is further suppressed, and repetition rate as high as 1.1 GHz is demonstrated.