We report what is to our knowledge the lowest phase and amplitude noise characteristics achieved to date in a 10-GHz pulse train produced by the active harmonic mode locking of an external-cavity semiconductor diode laser. Supermode noise has also been suppressed below -140 dBc/Hz by use of a high-finesse fiber Fabry–Perot etalon as an intracavity filter. Novel noise sideband measurements that extend to the Nyquist offset frequency suggest a significant advantage in using harmonic (rather than fundamental) mode locking to produce ultralow-noise pulse trains, owing to the relationship between the noise roll-off frequency and the fundamental cavity frequency.
© 2002 Optical Society of America
C. M. DePriest, T. Yilmaz, P. J. Delfyett, Jr., S. Etemad, A. Braun, and J. Abeles, "Ultralow noise and supermode suppression in an actively mode-locked external-cavity semiconductor diode ring laser," Opt. Lett. 27, 719-721 (2002)