The observation of a novel noncollinear optical second-harmonic generation mechanism is reported. In strontium barium niobate crystals, a circular cone of second-harmonic light is generated when a fundamental beam of intensive laser light is directed along the crystallographic c axis. It can be shown that the effect is caused by the nonlinear polarization of antiparallel ordered ferroelectric microdomains.
The index of refraction, the optical band edge and the Raman scattering of strontium barium niobate, Sr x Ba 1-x Nb 2 O 6 with 0 38 0 77 x . < < . have been studied. The ordinary refractive index does not depend on x, while the extra-ordinary one increases with increasing x. The band edge is almost unaffected by the Baor Sr-content and shows a weak band bowing. Both the index of refraction and the band edge may be used for an optical determination of the composition of the crystal. Raman spectra show the typical behavior of tungsten bronze type crystals with broad bands and complicated spectral shapes.
The collective behavior of an ensemble of multimode stochastic oscillators is investigated. The oscillators are pulse coupled; they are able to emit pulses and to detect the pulses emitted by the others. As a function of the output intensity in the system they can operate in different modes having different pulsing periods. The system is designed to optimize the output intensity around a fixed f* output threshold. In order to do so a simple dynamics is considered. Whenever the total output intensity in the system is lower than f*, a mode with a higher interpulse period is chosen. If the light intensity in the system is higher than f*, a mode with a lower interpulse period is selected. As a side effect of this simple optimization rule, for a given f* interval a nontrivial synchronization of the oscillators is observed. The synchronization level is studied by computer simulations, investigating the influence of model parameters (number of modes, stochasticity of the oscillators, the f* threshold value, and interaction topology). An experimental realization of this system is also considered; an ensemble of electronic oscillators communicating with light pulses was constructed and studied. The experimental system behaves in many ways similar to the theoretically considered multimode stochastic oscillator ensemble.
The temperature dependence of the spontaneous polarization in strontium-barium-niobate single crystals with varying Sr/Ba ratio is presented. The temperature of the relaxor phase-transition is determined from the inflexion point of the curve of the ferroelectric polarization versus temperature. The influence of the Sr/Ba ratio in the crystal on the transition temperature is discussed within an effective field approach.
The 90°-light scattering on domain walls was probed in various strontium barium niobate ͑SBN͒ crystals for studies of the ferroelectric switching under pulsed fields. The validity of this optical method is proved by a good agreement of the switching parameters deduced from optical scattering data with those obtained with electric methods. Scanning of the scattering over the crystal bulk revealed local specialities of the switching, particularly, a marked distribution of the domain wall density D along the polar axis with a maximum close to the negative electrode. In compliance with these in situ observations, the electro-optic coefficient r c reveals a position dependence in all SBN crystals poled in the ferroelectric phase, r c decreasing from the positive to negative electrode. This regularity is interpreted in terms of the domain density distribution D͑z͒ and accounted for by an asymmetry of the domain nucleation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.