Localized vortices in semiconductor lasers (original) (raw)

Bistable and Addressable Localized Vortices in Semiconductor Lasers

Physical Review Letters, 2010

Beyond the chirality of light associated to polarization or spin, light beams can carry an additional orbital angular momentum due to the helicoidal structure of their phase front . This property, if combined with light localization could give rise to localized optical vortices , whose existence in nonlinear and dissipative optical systems is suggested by several theoretical studies . However, while several kinds of localized states have been experimentally found (see ), no observation of localized vortices have been reported to date. We demonstrate the existence of bistable and addressable chiral localized structures in a semiconductor laser with saturable absorber. For a fixed set of parameters, we observe localized states with positive or negative topological charge, both coexisting with a fundamental "off" state. In contrast with phase defects and vortex solitons (see for a review), the spatial structures described in this report are transversally localized and bistable due to the presence of dissipation. These properties, generically associated to localized structures, make localized vortices attractive for the realization of arrays of independant and controllable "doughnut shaped" beams which would dramatically enhance the efficiency of advanced optical nanoscopy techniques [10], especially in fast and compact sources such as semiconductor lasers.

Vortex modes supported by spin–orbit coupling in a laser with saturable absorption

New Journal of Physics

We introduce a system of two component two-dimensional (2D) complex Ginzburg-Landau equations with spin-orbit-coupling (SOC) describing a wide-aperture microcavity laser with saturable gain and absorption. We report families of two-component self-trapped dissipative laser solitons in this system. The SOC terms are represented by the second-order differential operators, which sets the difference, S 2 D = | | , between the vorticities of the two components. We have found stable solitons of two types: vortex-antivortex (VAV) and semi-vortex (SV) bound states, featuring vorticities 1, 1-+ ()and 0, 2 (), respectively. In previous works, 2D localized states of these types were found only in models including a trapping potential, while we are dealing with the self-trapping effect in the latteraly unconfined (free-space) model. The SV states are stable in a narrow interval of values of the gain coefficients. The stability interval is broader for VAV states, and it may be expanded by making SOC stronger (although the system without SOC features a stability interval too). We have found three branches of stationary solutions of both VAV and SV types, two unstable and one stable. The latter one is an attractor, as the unstable states spontaneously transform into the stable one, while retaining vorticities of their components. Unlike previously known 2D localized states, maintained by the combination of the trapping potential and SOC, in the present system the VAV and SV complexes are stable in the absence of diffusion. In contrast with the bright solitons in conservative models, chemical potentials of the dissipative solitons reported here are positive.

Cavity Soliton Laser based on coupled micro-resonators

Localized States in Physics: Solitons and Patterns, 2010

We describe the experimental observation of self localized laser sources in a compound laser system consisting of two mutually coupled broad area Vertical Cavity Surface Emittng Lasers (VCSELs), one of which is used as a saturable absorber. The observed structures coexist with a dark homogeneous background and they share some properties with cavity solitons (CS) in VCSEL with coherent driving beam. By exploring the large parameter space to map the region of existence of cavity soliton solutions, we obtained multi-peaks cavity solitons and ring-like localized laser states. We therefore address the problem of the bifurcation diagram associated to the formation of these composite states in a laser scheme. All of the complex structures can be switched by means of a local addressing beam. The long external self-imaging cavity scheme allows for laser solitons to have multistable emission frequencies.

Mutual coherence of laser solitons in coupled semiconductor resonators

The European Physical Journal D, 2010

Laser solitons are bistable localized laser beams that can be independently addressed by a local optical perturbation in form of a narrow beam. They can form in the transverse section of broad-area laser systems when suitable conditions are created. At difference with cavity solitons in driven microresonator, their phase is not fixed by any driving field and therefore no fixed phase relation between laser solitons should be expected. In this paper we analyze experimentally the mutual coherence of single-peak laser solitons and of multi-peaks laser solitons or clusters that coexist in the output beam of a laser system. We show that independent laser solitons are not mutually coherent while the peaks of a cluster have a well established mutual phase relationship.

Cavity solitons in two-level lasers with dense amplifying medium

2003

Local-field effects are known to induce bistability in dense optical media. We examine theoretically whether this property is preserved in broad-area cavities, and show that bistability between the homogeneous lasing and nonlasing states of the system persists provided a Fourier filtering technique is used to prevent off-axis emission. The resulting bistability gives rise to spatial light localization in the form of cavity solitons, which exhibit a particularly large degree of plasticity as a function of the characteristics of the addressing beam. This is the simplest laser able to sustain cavity solitons.

Two-photon cavity solitons in a laser: radiative profiles, interaction and control

Journal of Optics B: Quantum and Semiclassical Optics, 2004

We study the properties of two-photon cavity solitons that appear in a broad-area cascade laser. These vectorial solitons consist of islands of two-photon emission emerging over a background of single-photon emission. Analysis of their structural properties reveals singular features such as their short distance radiation of outgoing waves, which can be interpreted in terms of the soliton frequency profile. However, the phase of these solitons is not determined by any external factor, which influences the way in which the structures can be written and erased. We also examine ways of controlling the cavity-soliton position, and analyse the interaction between neighbouring cavity solitons. Finally, investigation of the parameter dependence of these structures shows a route from soliton-dominated to defect-mediated turbulence.

Frequency and Phase Locking of Laser Cavity Solitons

Progress in Optical Science and Photonics, 2012

Self-localized states or dissipative solitons have the freedom of translation in systems with a homogeneous background. When compared to cavity solitons in coherently driven nonlinear optical systems, laser cavity solitons have the additional freedom of the optical phase. We explore the consequences of this additional Goldstone mode and analyze experimentally and numerically frequency and phase locking of laser cavity solitons in a vertical-cavity surface-emitting laser with frequency-selective feedback. Due to growth-related variations of the cavity resonance, the translational symmetry is usually broken in real devices. Pinning to different defects means that separate laser cavity solitons have different frequencies and are mutually incoherent. If two solitons are close to each other, however, their interaction leads to synchronization due to phase and frequency locking with strong similarities to the Adler-scenario of coupled oscillators.

Interaction of oscillatory and excitable dissipative solitons in a nonlinear optical cavity

The interaction between stationary localized states have long been studied, but localized states may undergo a number of instabilities that lead to more complicated dynamical regimes. In this case, the effects of the interaction are much less known. This chapter addresses the problem of the interaction between oscillatory and excitable localized states in a Kerr cavity. These oscillatory structures can be considered as non punctual oscillators with a highly non-trivial spatial coupling, which leads to rather complicated dynamics beyond what can be explained in terms of simple coupled oscillators. We also explore the possibility of using coupled excitable localized structures to build all-optical logical gates.