Detailed experimental and theoretical investigations of two coupled fiber lasers, each with many longitudinal modes, reveal that the behavior of the longitudinal modes depends on both the coupling strength and the detuning between them. For low to moderate coupling strength only longitudinal modes that are common for both lasers phase lock, while those that are not common gradually disappear. For larger coupling strengths, the longitudinal modes that are not common reappear and phase lock. When the coupling strength approaches unity the coupled lasers behave as a single long cavity with correspondingly denser longitudinal modes. Finally, we show that the gradual increase in phase locking as a function of the coupling strength results from competition between phase-locked and non-phase-locked longitudinal modes.
© 2010 Optical Society of America
Lasers and Laser Optics
Original Manuscript: December 2, 2009
Revised Manuscript: December 29, 2009
Manuscript Accepted: January 4, 2010
Published: February 9, 2010
Moti Fridman, Micha Nixon, Eitan Ronen, Asher A. Friesem, and Nir Davidson, "Phase locking of two coupled lasers with many longitudinal modes," Opt. Lett. 35, 526-528 (2010)