Locking Phenomena in Semiconductor Lasers near Threshold with Optical Feedback and Sinusoidal Current Modulation

Jordi Tiana-Alsina,Cristina Masoller

doi:10.3390/app11177871

Jordi Tiana-Alsina, Cristina Masoller

Open Access

https://doi.org/10.3390/app11177871

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Abstract

The dynamics of semiconductor lasers with optical feedback and current modulation has been extensively studied, and it is, by now, well known that the interplay of modulation and feedback can produce a rich variety of nonlinear phenomena. Near threshold, in the so-called low frequency fluctuations regime, the intensity emitted by the laser, without modulation, exhibits feedback-induced spikes, which occur at irregular times. When the laser current is sinusoidally modulated, under appropriate conditions, the spikes lock to the modulation and become periodic. In previous works, we studied experimentally the locked behavior and found sub-harmonic locking (regular spike timing such that a spike is emitted every two or three modulation cycles), but we did not find spikes with regular timing, emitted every modulation cycle. To understand why 1:1 regular locking was not observed, here, we perform simulations of the well-known Lang–Kobayashi model. We find a good qualitative agreement with the experiments: with small modulation amplitudes, we find wide parameter regions in which the spikes are sub-harmonically locked to the modulation, while 1:1 locking occurs at much higher modulation amplitudes.

Highlights

We have found that small-amplitude sinusoidal current modulation can generate rigid and regular subharmonically locked spikes: rigid in the sense that the locked behavior persists in a parameter region, and regular in the sense that the spike timing is regular over very long time intervals [21]
We have studied numerically the dynamics of a semiconductor laser with optical feedback and sinusoidal current modulation
We have found 1:1 locked spikes that occur at a higher modulation amplitude and lower modulation frequency, but in this case, the spike timing is more irregular

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Semiconductor lasers with optical feedback provide an experimental testbed to study a rich variety of nonlinear phenomena. While the free-running laser is a two-dimensional system that displays only transient relaxation oscillations, the feedback delay time expands the dimensionality of the system, and induces multistability of stable solutions (the so-called external cavity modes) and sustained periodic or chaotic oscillations [1,2,3]. A small-amplitude periodic modulation of the laser current can control feedback-induced oscillations, but it can generate bistability, for example, of small and large chaotic oscillations [4]

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