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53. Soliton dynamics of ring quantum cascade lasers with injected signal.

Author

Prati, Franco, Brambilla, Massimo, Piccardo, Marco, Columbo, Lorenzo Luigi, Silvestri, Carlo, Gioannini, Mariangela, Gatti, Alessandra, Lugiato, Luigi A., and Capasso, Federico

Subjects
QUANTUM rings, QUANTUM cascade lasers, OPTICAL bistability, QUANTUM theory, OPTICAL solitons, MODULATIONAL instability, SYMMETRY breaking, OPTICS
Abstract

Nonlinear interactions in many physical systems lead to symmetry breaking phenomena in which an initial spatially homogeneous stationary solution becomes modulated. Modulation instabilities have been widely studied since the 1960s in different branches of nonlinear physics. In optics, they may result in the formation of optical solitons, localized structures that maintain their shape as they propagate, which have been investigated in systems ranging from optical fibres to passive microresonators. Recently, a generalized version of the Lugiato–Lefever equation predicted their existence in ring quantum cascade lasers with an external driving field, a configuration that enables the bistability mechanism at the basis of the formation of optical solitons. Here, we consider this driven emitter and extensively study the structures emerging therein. The most promising regimes for localized structure formation are assessed by means of a linear stability analysis of the homogeneous stationary solution (or continuous-wave solution). In particular, we show the existence of phase solitons – chiral structures excited by phase jumps in the cavity – and cavity solitons. The latter can be deterministically excited by means of writing pulses and manipulated by the application of intensity gradients, making them promising as frequency combs (in the spectral domain) or reconfigurable bit sequences that can encode information inside the ring cavity. [ABSTRACT FROM AUTHOR]

Published
2021
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70. Cavity Solitons

Author

Lugiato, L., Prati, Franco, Brambilla, M., Columbo, LORENZO LUIGI, Barland, S., Tissoni, GIOVANNA LIA, Aghdami, K., Kheradmand, R., Tajalli, H., and Vahed, H.

Published
2013
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71. Polarization Dynamics of VCSELs

Author

Panayotov, Krassimir, Prati, Franco, Michalzik, Rainer, Applied Physics and Photonics, and Brussels Photonics Team

Abstract

In this chapter we wrap up the experimental and theoretical results on polarization dynamics of solitary vertical-cavity surface-emitting lasers. Experiments have shown that VCSELs emit a linearly polarized fundamental transverse mode either along the [110] or [1-10] crystallographic direction. Polarization switching between these modes can occur when the injection current is increased, showing either a frequency shift from the higher to the lower frequency mode (type I) or the reverse (type II). The two modes of linear polarization are strongly anti-correlated. The switching can happen through a region of mode hopping, with a dwell time scaling over eight orders of magnitude with the switching current, or through a region of hysteresis. Thermal (carrier) effects influence the polarization behavior of VCSELs through a red (blue) shift of the gain maximum. Also, in-plane anisotropic strain can strongly modify the polarization behavior of VCSELs. All these experimental results call for explanations, as there is no a priori intrinsic polarization selection mechanism in VCSELs. We present different gain equalization models to explain type I, type II or double polarization switching. Alternatively, the spin-flip model can explain both types polarization switching by involving a microscopic spin-flip relaxation mechanism. Its predictive power has been experimentally established.

Published
2013

99. Preface

Author

Lugiato, Luigi, primary, Prati, Franco, additional, and Brambilla, Massimo, additional

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