Light-induced refractive index changes in LiNbO3:Ti waveguides

Experimental Observation of Rabi Oscillations in Photonic Lattices

“…The grating vector K is aligned at an angle ' relative to the z direction, i.e., tanð'Þ ¼ Ák x =Á, with Ák x and Á being the transverse and longitudinal components of K, respectively. In this scheme, the photorefractive properties of our sample are periodically modulated: the concentration of the photorefractive centers (Fe 2þ and Fe 3þ ) is periodically modulated along x due to the modulated Ti concentration forming the array [11]. When illuminated with a uniform intensity, such modulated trap densities lead to modulated photovoltaic currents [12], which in turn generate a modulated refractive-index change, in this case in the x direction, of the same spatial modulation as the permanent lattice modulation ÁnðxÞ.…”

Increased photorefractive sensitivity in double-doped KTa_1−xNbxO_3:Fe,Ti

“…4 In LiNbO 3 waveguides, Ti indiffusion leads to a reduction of the valence state of Fe impurities and to a resultant increase in photorefractive damage. 5 In this Letter we describe results in which The absorption spectrum of each sample was measured with a double-beam spectrophotometer, and all the spectra are shown in Fig. 1.…”

“…It can also be applied to other host crystals, including KNbO 3 , LiTaO 3 , and LiNbO 3 , in which the effect has been observed in Ti-indiffused waveguides. 5 The photorefractive properties of Fe-doped, Tidoped, and Fe-and Ti-double-doped KTN samples were investigated. Absorption measurements indicate that the double-dopant combination of Fe and Ti increases the fraction of Fe in the reduced Fe 2 + valence state and increases the fraction of Fe that enters the crystal from the flux compared with that of single-doped Fe sample.…”

Photorefractive Waveguides

“…However, in most investigations of photorefractive waveguides, averaged quantities have been used to describe both, the light distribution inside the sample and the photorefractive properties. Examples are effective widths and propagation depths of the excited modes, averaged light intensities, or refractive index changes and photovoltaic constants where the values are averaged over the depth of the waveguiding layer [6]. For these averaged quantities, the Kogelnik theory of the interaction of plane waves can be used to interpret the results.…”

“…It has been recognized that Fe 2þ centers are stabilized by Ti 4þ ions against oxidation [6], thus increasing the sensitivity to optical damage. On the other hand, a higher photorefractive damage resistance has been obtained for waveguides prepared by the diffusion of zinc into LiNbO 3 and for moderate light intensities of the order of 10 5 W=cm 2 [31].…”