The Ising–Bloch transition in degenerate optical parametric oscillators
Domain walls in type I degenerate optical parametric oscillators are numerically investigated. Both steady Ising and moving Bloch walls are found, bifurcating one into another through a nonequilibrium Ising--Bloch transition. Bloch walls are found that connect either homogeneous or roll planforms. Secondary bifurcations affecting Bloch wall movement are characterized that lead to a transition from a steady drift state to a temporal chaotic movement as the system is moved far from the primary, Ising--Bloch bifurcation. Two kinds of routes to chaos are found, both involving tori: a usual Ruelle-Takens and an intermittent scenarios.
Quantum noise properties of cavity solitons
General method for studying quantum fluctuations of dissipative structures formed in nonlinear optical cavities is presented. Application to cavity soliton supported by degenerate optical parametric oscillator is presented. Squeezing and intensity fluctuations spectra are discussed.
Low frequencies noise effects on behaviour of Sparus aurata juveniles
Human activities in the oceans, such as marine traffic and Deep Sea Mining (DSM), are increasing in the last years (Ross 2005; Calvo et al 2016). Underwater noise in the oceans, especially at lower frequencies, is mainly produced by marine traffic and DSM could increase this noise in the next future. Marine Strategy Framework Directive promotes the achievement of a good quality environmental status and aims to monitor “continuous low frequency sound” trend in the ambient noise level within the 1/3 octave bands centred at 63 and 125 Hz. The aim of this study is to evaluate the behavioural changes of Sparus aurata juveniles exposed to a four different acoustic signals in a tank. The emitted s…
Domain wall dynamics in an optical Kerr cavity
An anisotropic (dichroic) optical cavity containing a self-focusing Kerr medium is shown to display a bifurcation between static --Ising-- and moving --Bloch-- domain walls, the so-called nonequilibrium Ising-Bloch transition (NIB). Bloch walls can show regular or irregular temporal behaviour, in particular, bursting and spiking. These phenomena are interpreted in terms of the spatio-temporal dynamics of the extended patterns connected by the wall, which display complex dynamical behaviour as well. Domain wall interaction, including the formation of bound states is also addressed.
Cavity solitons in bidirectional lasers.
We show theoretically that a broad area bidirectional laser with slightly different cavity losses for the two counterpropagating fields sustains cavity solitons (CSs). These structures are complementary, i.e., there is a bright (dark) CS in the field with more (less) losses. Interestingly, the CSs can be written/erased by injecting suitable pulses in any of the two counterpropagating fields.
Stabilizing and controlling domain walls and dark-ring cavity solitons.
We demonstrate two alternative techniques for controlling and stabilizing domain walls (DW) in phase-sensitive, nonlinear optical resonators. The first of them uses input pumps with spatially modulated phase and can be applied also to dark-ring cavity solitons. An optical memory based on the latter is demonstrated. Here the physical mechanism of control relies on the advection caused to any feature by the phase gradients. The second technique uses a plane wave input pump with holes of null intensity across its transverse plane, which are able to capture DWs. Here the physical mechanism of control is of topological nature. When distributed as a regular array, these holes delimit spatial opti…
Theory of quantum fluctuations of optical dissipative structures - Application to the study of squeezing and intensity fluctuations of DOPO cavity solitons
We present a general theory of quantum fluctuations of dissipative structures in nonlinear optical cavities with transverse translation invariance. Perfect squeezing of the transverse momentum, detectable under homodyning, occurs irrespectively of the system parameters.
Vectorial Kerr-cavity solitons.
It is shown that a Kerr cavity with different losses for the two polarization components of the field can support both dark and bright cavity solitons (CS’s). A parametrically driven Ginzburg–Landau equation is shown to describe the system for large-cavity anisotropy. In one transverse dimension the nonlinear dynamics of the bright CS’s is numerically investigated.
Theory of quantum fluctuations of optical dissipative structures and its application to the squeezing properties of bright cavity solitons
We present a method for the study of quantum fluctuations of dissipative structures forming in nonlinear optical cavities, which we illustrate in the case of a degenerate, type I optical parametric oscillator. The method consists in (i) taking into account explicitly, through a collective variable description, the drift of the dissipative structure caused by the quantum noise, and (ii) expanding the remaining -internal- fluctuations in the biorthonormal basis associated to the linear operator governing the evolution of fluctuations in the linearized Langevin equations. We obtain general expressions for the squeezing and intensity fluctuations spectra. Then we theoretically study the squeezi…
Spontaneous symmetry breaking as a resource for noncritically squeezed light
[EN] In the last years we have proposed the use of the mechanism of spontaneous symmetry breaking with the purpose of generating perfect quadrature squeezing. Here we review previous work dealing with spatial (translational and rotational) symmetries, both on optical parametric oscillators and four-wave mixing cavities, as well as present new results. We then extend the phenomenon to the polarization state of the signal field, hence introducing spontaneous polarization symmetry breaking. Finally we propose a Jaynes-Cummings model in which the phenomenon can be investigated at the singlephoton-pair level in a non-dissipative case, with the purpose of understanding it from a most fundamental …
Diffusion stabilizes cavity solitons in bidirectional lasers
We study the influence of field diffusion on the spatial localized structures (cavity solitons) recently predicted in bidirectional lasers. We find twofold positive role of the diffusion: 1) it increases the stability range of the individual (isolated) solitons; 2) it reduces the long-range interaction between the cavity solitons. Latter allows the independent manipulation (writing and erasing) of individual cavity solitons.
Domain walls and ising-BLOCH transitions in parametrically driven systems.
Parametrically driven systems sustaining sech solitons are shown to support a new kind of localized state. These structures are walls connecting two regions oscillating in antiphase that form in the parameter domain where the sech soliton is unstable. Depending on the parameter set the oppositely phased domains can be either spatially uniform or patterned. Both chiral (Bloch) and nonchiral (Ising) walls are found, which bifurcate one into the other via an Ising-Bloch transition. While Ising walls are at rest Bloch walls move and may display secondary bifurcations leading to chaotic wall motion.
The effect of low frequency noise on the behaviour of juvenile Sparus aurata.
[EN] Anthropogenic activities are causing increased noise levels in the marine environment. To date, few studies have been undertaken to investigate the effects of different noise frequencies on the behaviour of juvenile fish. In this study, the behavioural changes of juvenile gilthead seabream (Sparus aurata) are evaluated when exposed to white noise filtered in third-octave bands centred at 63, 125, 500, and 1000 Hz (sound pressure level, 140-150 dB re 1 mu& x3a1;a) for 7 h. The group dispersion, motility, and swimming height of the fish were analysed before and during the acoustic emission. Dispersion of the fish was found to reduce immediately upon application of low frequency sound (63…
Ultrasonic cavity solitons
We report on a new type of localized structure, an ultrasonic cavity soliton, supported by large aspect-ratio acoustic resonators containing viscous media. These states of the acoustic and thermal fields are robust structures, existing whenever a spatially uniform solution and a periodic pattern coexist. Direct proof of their existence is given both through the numerical integration of the model and through the analysis and numerical integration of a generalized Swift-Hohenberg equation, derived from the microscopic equations under conditions close to nascent bistability. An analytical solution for the ultrasonic cavity soliton is given.
Anthropogenic noise: the behavioural responses of Sparus aurata juveniles as the basis for a numerical model.
Underwater noise is mainly produced by anthropogenic activities and has increased in recent years. The Marine Strategy Framework Directive aims to monitor “continuous low frequency sound” trends in ambient noise in particular at 1/3rd octave bands centered at 63 and 125 Hz. The aim of this work is to evaluate the possibility of using the results of Sparus aurata juvenile’s behavior for parameterizing a numerical model of the fish behavior. The fishes were stressed with white noise filtered with a band pass filter at 1/3 octave band centered respectively at 63 Hz, 125 Hz, 500 Hz, and 1 kHz (SPL: 140-150 dB re 1µPa). We performed three test replicas for the control (without any sound emission…
Quadrature and polarization squeezing in a dispersive optical bistability model
We theoretically study quadrature and polarization squeezing in dispersive optical bistability through a vectorial Kerr cavity model describing a nonlinear cavity filled with an isotropic chi(3) medium in which self-phase and cross-phase modulation, as well as four--wave mixing, occur. We derive expressions for the quantum fluctuations of the output field quadratures as a function of which we express the spectrum of fluctuations of the output field Stokes parameters. We pay particular attention to study how the bifurcations affecting the non-null linearly polarized output mode squeezes the orthogonally polarized vacuum mode, and show how this produces polarization squeezing.
Quantum fluctuations in cavity solitons
Quantum fluctuations of degenerate optical parametric oscillators' cavity solitons (CS) are studied. We show that CSs are sources of perfectly squeezed light that exhibit photon fluctuations below the shot-noise level as well.