Delay induced high order locking effects in semiconductor lasers

Abstract

Multiple time scales appear in many nonlinear dynamical systems. Semiconductor lasers, in particular, provide a fertile testing ground for multiple time scale dynamics. For solitary semiconductor lasers, the two fundamental time scales are the cavity repetition rate and the relaxation oscillation frequency which is a characteristic of the field-matter interaction in the cavity. Typically, these two time scales are of very different orders, and mutual resonances do not occur. Optical feedback endows the system with a third time scale: the external cavity repetition rate. This is typically much longer than the device cavity repetition rate and suggests the possibility of resonances with the relaxation oscillations. We show that for lasers with highly damped relaxation oscillations, such resonances can be obtained and lead to spontaneous mode-locking. Two different laser types--a quantum dot based device and a quantum well based device-are analysed experimentally yielding qualitatively identical dynamics. A rate equation model is also employed showing an excellent agreement with the experimental results.

Routes to Chaos of a Semiconductor Laser Subjected to External Optical Feedback: A Review

“…[18], different ECMs can be experimentally selected as starting states of bifurcation diagrams, resulting in different initial instabilities). Interestingly, similar locking has also been reported in quantum dot lasers subjected to optical feedback [25].…”

“…Detailed experimental reports and interpretation of the intensity, phase, and optical spectrum in the various regimes can be found in Refs. [16,17,24,25]; the main points are focused on here.…”

“…The quasiperiodic appearance in time therefore does not result from a torus that would have developed from two successive Hopf bifurcations of a given ECM, as would be expected in a traditional quasiperiodic (Ruelle-Takens or Curry-Yorke) route [26], but is rather the result of the interaction between two equilibria (ECMs). In addition, it is interesting to note that the high frequency of the QP regime is equal to a multiple of the delay frequency f τ that is close to f RO [25] and it remains locked to that multiple if the current, and thus f RO , is slightly varied. As the feedback is further increased, and region γ is reached, periodic LC dynamics, located on a single ECM, are observed, again with frequencies that are (different) multiples of f τ .…”

Resonances between fundamental frequencies for lasers with large delayed feedbacks

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High-order frequency locking phenomena were recently observed using semiconductor lasers subject to large delayed feedbacks [1,2]. Specifically, the relaxation oscillation (RO) frequency and a harmonic of the feedback-loop round-trip frequency coincided with the ratios 1:5 to 1:11.

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“…This work is further explored in Ref. [2] for both quantum dot and quantum well SLs. Resonant effects between fundamental frequencies in a delayed feedback laser system may sufficiently stabilize the laser output as has been recently demonstrated in Ref.…”