P. Jullien

Numerical analysis of a WKB inverse method in view of index profile reconstruction in diffused waveguides

A novel formulation of WKB inverse method is conducted and applied in view of index profile reconstruction in diffused waveguides. Systematic and local errors on the effective indices are investigated. The consequences on the index profile shapes are studied.

Influence of oxygen vacancies on the photorefractive effect in barium titanate single crystals

Abstract In this work the influence of the vacancies concentration in pure BaTiO3 single crystals is studied. It is shown that the oxidation and the reduction do not change the electrooptic coefficients. The reduction modifies the nature of the majority carriers. An evaluation of the trap density N is done.

Theoretical study of Fe doping and oxidation–reduction influence on the photorefractive effect in BaTiO 3

We numerically solve charge-transport and Poisson equations for photorefractive BaTiO3 single crystals with a band model, using four impurity levels, Fe2+–Fe3+, Fe3+–Fe4+, VO••–VO•, and VO•-VOx. Densities and photoinduced spatial distributions of each population are computed as a function of annealing O partial pressure. Space-charge field and beam-coupling gain are also computed as a function of annealing O partial pressure, temperature, Fe concentration, grating wave vector, and light intensity. We discuss the intervening mechanism of impurity centers and the correlations between experimental conditions of crystal growth, oxidation–reduction treatments, and measurement parameters.

Algebraic value of the electrooptic coefficients and nature of charge carriers in batio3 single crystals

Abstract Some monodomain pure and Fe doped barium titanate monocrystals are studied. The algebraic values of the electrooptic coefficients r 13 and r 33 are evaluated using an interferometric method. Then, from energy transfer results it is possible to conclude that majority carriers are positive charges in all the samples.

Energy leaks through the optical barrier created by H+ implantation in BaTiO3 and LiNbO3 planar waveguides

Abstract The energy leaks through the index barrier created by the proton implantation process are put in evidence in planar optical waveguides made in BaTiO 3 and LiNbO 3 substrates. The selective detection of the light emerging from the guiding region permits to measure the optical attenuation of the guided wave. The results obtained on mono or twice implanted LiNbO 3 and BaTiO 3 waveguides are presented and discussed. It is shown that the light confinement is better in BaTiO 3 than in LiNbO 3 .

Two-wave mixing at 854 nm in BaTiO3:Rh planar waveguide implanted with He+

Abstract Guided waves at 854 nm are observed in a BaTiO 3 :Rh waveguide fabricated by the technique of ion-beam implantation. The photorefractive interaction between two guided modes is demonstrated and characterized. The experiments reveal that the gain direction is reversed in the guiding layer in comparison with that in the bulk. A maximum gain of 24 cm −1 is achieved.

Theory of electro-optic effect in the tetragonal phase of BaTiO3

Abstract The microscopic mechanism of electro-optic effect in tetragonal phase of BaTiO3 is discussed taking account of the piezoelectric effect due to the lattice deformation and the spontaneous Kerr effect as to a cause of the to the strong local field acting in the constituant ions. It is found that the birefringence σn and the linear electro-optic coefficients (Pockels constants) r33 and r13 obtained are in good agreement with the experimental data.

Theoretical study of the electro-optic effect in the tetragonal phase of pure and Fe doped BaTiO3

Abstract The microscopic mechanism of electro-optic effect in tetragonal phase of monodomain pure and Fe doped barium titanate crystals is discussed taking account of the piezoelectric effect due to the lattice defomation and the spontaneous Kerr effect due to the strong local field acting on the constituent ions. It is found that the calculated birefringence δn and the linear electro-optic or Pockels constants r 33 and r 33 versus temperature and dopant concentration are in good agreement with the experimental data.

Photorefractive effect study in BaTiO3 by numerical computation of a four energy levels band model

Abstract This abstract work shows the results obtained on BaTiO3 single crystals with a band model using four impurity levels Fe2+/Fe3+, Fe3+/Fe4+, Vo/o/Vo o, Vo o/Vo o. Densities and photo-induced spatial distribution of: each center; space charge field and beam-coupling gain are computed as a function of annealing oxygen partial pressure, temperature and Fe-concentration. Theoretical study agrees very well with experimental results and gives infomations about correlation between the different growth parameters

Phase conjugation in BaTiO 3 by use of the indirect photorefractive coupling of orthogonally polarized light waves

A phase-conjugate wave is generated when an ordinary (extraordinary) signal wave is mixed with two counterpropagating extraordinary (ordinary) waves in the plane normal to the BaTiO3 polar axis. The photorefractive grating that couples the ordinary and the extraordinary waves appears if the incident waves induce a noticeable conical parametric scattering; this grating is a difference grating of many noisy scattering gratings recorded by means of the usual diffusion-mediated charge transport. For comparable intensities of signal and pump waves this type of nonlinear wave mixing is much more efficient than that which is due to the circular bulk photovoltaic effect.