We find that the anomalous behavior of optical spatial screening solitons observed in the high-symmetry paraelectric phase is a consequence of nonlinear dielectric effects. These, coupled to space charge in saturated conditions, change the effective optical nonlinearity even far from the phase-transition regime.
We demonstrate electro-optic spatial two-dimensional mode switching in a bulk sample of potassium lithium tantalate niobate. Spatial confinement, mode coupling, and electro-optic functionality are mediated by two photorefractive needle solitons of opposite electroholographic charges embedded together in their anisotropic lobular structure. (C) 2002 Optical Society of America.
Electroholography is a wavelength-selective optical switching method based on governing of the reconstruction process of volume holograms by means of an electric field. Electroholography is based on the voltage-controlled photorefractive effect in the paraelectric phase. The basic switching device is an electrically controlled Bragg grating or a volume hologram stored in a volume of a paraelectric crystal by the photorefractive process.
The basic electroholographic switching operation is the reconstruction of a volume grating (hologram), which requires that the Bragg condition be satisfied, and therefore is wavelength selective. In addition the applied field governs the efficiency of the reconstruction. Consequently, electroholographic switching includes grouping, multicasting, power management and non-intrusive data as an integral part of the switching operation. In preliminary measurements the performance envelope of the electroholography-based switch, is a cube of 1.8 mm3 was found to be as follows:
The minimum net insertion loss is 0.5 dB per switching operation. The minimum loss when a beam propagates through a latent grating is 0.2%. The Polarization-Dependent Loss (PDL) in a device that includes diversity architecture is less than 0.4 dB and the Polarization Mode Dispersion (PMD) is less than 0.07 ps. Bit-error rate (BER) in a switch operating at 40 Gb/s was measured to be 10-13. These features make electroholography ideal for circuit switching applications. Finally, response times of approximately 10 ns were measured, opening the way to burst switching applications.
Vladimir A Trepakov, Lubomir Jastrabik, Siegmar Kapphan, Enrico Giulotto, and Aharon J Agranat. 2002. “
Phase transitions, related properties and possible applications of (K,Li)(Ta,Nb)O3 crystals.” Optical Materials, 19, Photonic Materials for the 21st Century. Proceedings of the 2nd International Symposium on Laser, Scintillator and Nonlinear Opt, Pp. 13 - 21.
Publisher's Version Abstract It is shown that doping the highly polarizable KTaO3 perovskite simultaneously by Li and Nb (K1−xLixTa1−yNbyO3, KLTN) gives rise to new impressive dipole ordering effects, very unusual physical properties and strong responses with respect to doping parameters. Besides, KLTN has outstanding perspectives of application in electrically controlled holographic and compositionally graded pyroelectric devices.
Accession Number: S0925346701001963; Author: Trepakov, Vladimir A. (a, ∗); Author: Jastrabik, Lubomir (b); Author: Kapphan, Siegmar (c); Author: Giulotto, Enrico (d); Author: Agranat, Aharon J. (e); Affiliation: A.F. Ioffe Physical and Technical Institute, 194 021 St. Petersburg, Russia; Affiliation: Institute of Physics AS CR, 182 21 Praha 8, Czech Republic; Affiliation: FB Physik, University of Osnabrück, 49069 Osnabrück, Germany; Affiliation: Dipartimento di Fisica “A. Volta”, Università di Pavia and INFM, 27100 Pavia, Italy; Affiliation: Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel; Number of Pages: 9; Language: English;
The dielectric and ferroelectric properties of K1-xLixTa1-yNbyO3 (KLTN) crystals as functions of temperature, frequency, and electric field are presented. Measurement of the polarization as a function of temperature indicates the existence of polarized microregions at temperatures well above the phase transition (PT) temperature. In the vicinity of the PT those microregions respond cooperatively and contribute to the observed macroscopic polarization. This cooperative behavior was also evident from dielectric relaxation measurements. Two relaxation processes were observed, one at high frequency and the other at low frequency. In both processes the relaxation time and the relaxation step (DeltaE) were found to increase as the PT temperature was approached. Those processes originate from movement of off-center ions in a multi-well potential. In the vicinity of the PT the correlation length of the host lattice is increased and the movements of the off-center ions become more and more correlated. The increased number of cooperatively relaxing ions increases the relaxation time and the relaxation amplitude. (C) 2002 Published by Elsevier Science B.V.
