Square-wave oscillations in a semiconductor ring laser subject to counter-directional delayed mutual feedback

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Original languageEnglish
Pages (from-to)812-815
Journal / PublicationOptics Letters
Issue number4
Online published10 Feb 2016
Publication statusPublished - 15 Feb 2016


Square-wave (SW) switching of the lasing direction in a semiconductor ring laser (SRL) is investigated using counter-directional mutual feedback. The SRL is electrically biased to a regime that supports lasing in either counter-clockwise (CCW) or clockwise (CW) direction. The CCW and CW modes are then counter-directionally coupled by optical feedback, where the CCW-to-CW and CW-to-CCW feedback are delayed by τ1 and τ2, respectively. The mutual feedback invokes SW oscillations of the CCW and CW emission intensities with a period of T ≈ τ1 + τ2. When τ1 = τ2, symmetric SWs with a duty cycle of 50% are obtained, where the switching time and electrical linewidth of the SWs can be reduced to, respectively, 1.4 ns and 1.1 kHz by strengthening the feedback. When τ1 ≠ τ2, asymmetric SWs are obtained with a tunable duty cycle of τ∕ (τ1 + τ2). High-order symmetric SWs with a period of T = (τ1 + τ2) ∕ n can also be observed for some integer n. Symmetric SWs of order =13 with a period of T =10.3 ns are observed experimentally.

Research Area(s)

  • Semiconductor lasers, Lasers, ring, Instabilities and chaos