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- Mercedes Carrascosa, Javier Villarroel, José Antonio Carnicero, Ángel García-Cabañes, J. M. González Cabrera
- Optics express
- 2008

The appearance of light intensity thresholds for catastrophic optical damage in LiNbO3 is satisfactorily explained by using a photorefractive model based on the Fe(2+)?Fe(3+) and NbLi(4+)?NbLi(5+) defect pairs. Model simulations of the photorefractive amplification gain as a function of the light intensity present sharp threshold behavior. A similar… (More)

- Javier Villarroel, José Antonio Carnicero, +5 authors B. Ramiro
- Optics express
- 2010

Photorefractive optical damage of single beams in LiNbO(3) crystals is analyzed within a framework of two photoactive centres (Fe(2+)/Fe(3+) and Nb(Li) (4+)/Nb(Li) (5+)). It compares model simulations and significant experimental measurements in LiNbO(3) waveguides. A good agreement is found in the performed comparisons: photovoltaic currents, refractive… (More)

The operation of photovoltaic (PV) tweezers, using the evanescent light-induced PV fields to trap and pattern nano- and micro-meter particles on a LiNbO(3) crystal surface, is discussed. The case of a periodic light pattern is addressed in detail, including the role of particle shape and the modulation index of the light pattern. The use of a single… (More)

- Miquel Montero, Javier Villarroel
- Physical review. E, Statistical, nonlinear, and…
- 2013

In this paper we consider a stochastic process that may experience random reset events which suddenly bring the system to the starting value and analyze the relevant statistical magnitudes. We focus our attention on monotonic continuous-time random walks with a constant drift: The process increases between the reset events, either by the effect of the… (More)

- Fernanda Luisa LÜDTKE, Javier Villarroel, Ángel García-Cabañes, Karsten Buse, Mercedes Carrascosa
- Optics express
- 2009

An interferometric Mach-Zehnder technique very recently developed has been applied to measure photorefractive index changes in different types of z-cut proton-exchanged planar waveguides in LiNbO(3). These measurements are complemented by determining the intensitythreshold for the onset of optical damage with a standard single-beam setup. In the intensity… (More)

- Javier Villarroel
- SIAM Journal of Applied Mathematics
- 1998

The “elliptic” version of a three-dimensional nonlinear integrable equation, the Toda chain equation, is studied by means of the inverse scattering method. Several classes of decaying solutions corresponding to both the continuous and discrete spectrum of the associated spectral problem are obtained. Conditions that guarantee reality and analyticity along… (More)

We consider the solution to Burger’s equation coupled to a stochastic noise in Ito’s sense. The main random properties of the wave are determined. The solution is related to a deterministic problem with a rescaled diffusion coefficient. Depending on the value of a parameter, the initial value problem may be ill posed, well posed up to an explosion time, or… (More)

- Francesca Mereu, Javier Villarroel
- IJART
- 2014

The usual development of the continuous-time random walk (CTRW) proceeds by assuming that the present is one of the jumping times. Under this restrictive assumption integral equations for the propagator and mean escape times have been derived. We generalize these results to the case when the present is an arbitrary time by recourse to renewal theory. The… (More)

- Miquel Montero, Javier Villarroel
- Physical review. E
- 2016

In this paper we consider a particular version of the random walk with restarts: random reset events which suddenly bring the system to the starting value. We analyze its relevant statistical properties, like the transition probability, and show how an equilibrium state appears. Formulas for the first-passage time, high-water marks, and other extreme… (More)