Open AccessSquare-wave oscillations in semiconductor ring lasers with delayed optical feedback
Author(s) -
Lilia Mashal,
Guy Van der Sande,
Lendert Gelens,
Jan Danckaert,
Guy Verschaffelt
Publication year - 2012
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.20.022503
Subject(s) - physics , lasing threshold , semiconductor laser theory , optics , laser , square (algebra) , noise (video) , asymmetry , coupling (piping) , square wave , semiconductor , materials science , optoelectronics , quantum mechanics , geometry , mathematics , voltage , artificial intelligence , computer science , metallurgy , image (mathematics)
We analyze experimentally and theoretically the effects of delayed optical cross-feedback in semiconductor ring lasers. We show that under appropriate conditions, feeding of only one directional mode back into the counter-propagating mode leads to square-wave oscillations. In this regime, the laser switches regularly between the two counter-propagating modes with a period close to twice the roundtrip time in the external feedback loop. We find that these oscillations are robust and appear for a wide range of parameters as long as a small asymmetry in the linear coupling between both modes is present. We show that by increasing the feedback strength or the injection current, the square-wave oscillations gradually disappear. Due to noise, mode-hopping between stable lasing in one directional mode and square wave oscillations is observed in this transition region.