Emergence of resonant mode-locking via delayed feedback in quantum dot semiconductor lasers

Abstract

Abstract:With conventional semiconductor lasers undergoing external optical feedback, a chaotic output is typically observed even for moderate levels of the feedback strength. In this paper we examine single mode quantum dot lasers under strong optical feedback conditions and show that an entirely new dynamical regime is found consisting of spontaneous mode-locking via a resonance between the relaxation oscillation frequency and the external cavity repetition rate. Experimental observations are supported by detailed numerical simulations of rate equations appropriate for this laser type. The phenomenon constitutes an entirely new mode-locking mechanism in semiconductor lasers.

Delay induced high order locking effects in semiconductor lasers

“…We examine the evolution of the pulse train found in Ref. 19 as the feedback strength is increased, finding a splintering of modal groups leading eventually to chaos. To investigate the generality of the phenomenon, we also examine a different device type-a multiquantum well device with a high RO damping.…”

“…[16][17][18] In Ref. 19, a resonance between the ROs and the ECMs was observed using a long external cavity and an InAs based QD device. It led to a resonant mode-locking where the RO frequency and a harmonic of the round-trip frequency coincided yielding a periodic train of pulses.…”

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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“…(B10) and (B11) are easily solved. We find three families of solutions given by (1): σθ = 2nπ (n = 1, ...), and σ = 1, (B13) (2): σθ = (2n + 1)π (n = 0, 1, ...)…”

“…The ratio f delay /f RO was in the range 10-30. More recently, this question reappeared in a series of experiments carried on a quantum dot laser subject to optical feedback and partial filtering [1]. The delay was large and the ratio f RO /f delay was close to an integer n. The authors reported on a Hopf bifurcation to sustained RO oscillations followed by a secondary bifurcation to quasi-periodic oscillations as the feedback parameter is progressively increased.…”