Broad Repetition-Rate Tunable Quantum-Dot External-Cavity Passively Mode-Locked Laser with Extremely Narrow Radio Frequency Linewidth

We report on a systematic investigation of a repetition-rate-tunable quantum-dot external-cavity passively mode-locked laser with a quasi-continuous frequency tuning range from 1 GHz to a record-low value of 191 MHz. A nearly constant pulse peak power at the different pulse repetition rates is revealed in the continuous frequency tuning range. The trend and optimization of the stable fundamental mode-locking are presented and interpreted. An RF linewidth of a record value of similar to 30 Hz is demonstrated, which indicates the low noise operation and high stability of the quantum-dot external-cavity passively mode-locked laser. (C) 2011 The Japan Society of Applied Physics