Isabel Pérez-Arjona

Theoretical prediction of the nondiffractive propagation of sonic waves through periodic acoustic media

We predict theoretically the nondiffractive propagation of sonic waves in periodic acoustic media (sonic crystals), by expansion into a set of plane waves (Bloch mode expansion), and by finite difference time domain calculations of finite beams. We also give analytical evaluations of the parameters for nondiffractive propagation, as well as the minimum size of the nondiffractively propagating acoustic beams.

Self collimation of ultrasound in a three-dimensional sonic crystal

We present the experimental demonstration of self-collimation (subdiffractive propagation) of an ultrasonic beam inside a three-dimensional (3D) sonic crystal. The crystal is formed by two crossed steel cylinders structures in a woodpilelike geometry disposed in water. Measurements of the 3D field distribution show that a narrow beam, which diffractively spreads in the absence of the sonic crystal, is strongly collimated in propagation inside the crystal, demonstrating the 3D self-collimation effect.

Elastic waves in phononic monolayer granular membranes

The vibrational properties of out-of-plane elastic waves in hexagonal monolayer granular membranes were studied theoretically. The predicted propagation modes involve an out-of-plane displacement and two rotations with axes in the membrane plane. Shear and bending rigidities at the contact between beads were considered. Both the cases of freely suspended membranes and membranes coupled to a rigid substrate were analyzed. Dispersion relations and the existence of band gaps are presented and discussed for various contact properties. For freely suspended membranes with sufficient contact bending rigidity, it is shown that complete band gaps exist. The results obtained may be of interest for testing with acoustic waves the elasticity of recently developed granular membranes composed of nanoparticles (of interest because of their phoxonic properties) and more generally for the control of designing devices for membrane wave propagation.

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 (CSs). 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 CSs is numerically investigated.

Quantum squeezing of optical dissipative structures

We show that any optical dissipative structure supported by degenerate optical parametric oscillators contains a special transverse mode that is free from quantum fluctuations when measured in a balanced homodyne detection experiment. The phenomenon is not critical as it is independent of the system parameters and, in particular, of the existence of bifurcations. This result is a consequence of the spatial symmetry breaking introduced by the dissipative structure. Effects that could degrade the squeezing level are considered.

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 are complementary; i.e., there is a bright (dark) CS in the field with larger (smaller) losses. Interestingly, the CSs can be written or erased by injecting suitable pulses into any of the two counterpropagating fields.

Simultaneous self-collimation of fundamental and second-harmonic in sonic crystals

Simultaneous self-collimation of sound beams with different frequencies, corresponding to fundamental wave and to its second harmonic, is proposed theoretically and demonstrated experimentally. The result is obtained when the isofrequency contours for each harmonics, corresponding to different propagation bands, develop flat segments along the same direction. The effect can be utilized for managing (enhancement and control) of nonlinear frequency mixing of narrow sound beams.

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.

Self-organization of ultrasound in viscous fluids

We report the theoretical and experimental demonstration of pattern formation in acoustics. The system is an acoustic resonator containing a viscous fluid. When the system is driven by an external periodic force, the ultrasonic field inside the cavity experiences different pattern-forming instabilities leading to the emergence of periodic structures. The system is also shown to possess bistable regimes, in which localized states of the ultrasonic field develop. The thermal nonlinearity in the viscous fluid, together with the far-from-equilibrium conditions, are responsible of the observed effects.

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