Visible to NIR inorganic perovskite with reduced lead and high PV performance.

We report the spontaneous formation of a volume cubic grating in ferroelectric KLTN. Diffraction indicates a 3D linear, electro-optic, and nonlinear structure with lattice constant 10000 times larger than the underlying perovskite lattice.

We study theoretically and experimentally the propagation of optical solitons in a lattice nonlinearity, a periodic pattern that both affects and is strongly affected by the wave. Observations are carried out using spatial photorefractive solitons in a volume microstructured crystal with a built-in oscillating low-frequency dielectric constant. The pattern causes an oscillating electro-optic response that induces a periodic optical nonlinearity. On-axis results in potassium-lithium-tantalate-niobate indicate the appearance of effective continuous saturated-Kerr solitons, where all spatial traces of the lattice vanish, independently of the ratio between beam width and lattice constant. Decoupling the lattice nonlinearity allows the detection of discrete delocalized and localized light distributions, demonstrating that the continuous solitons form out of the combined compensation of diffraction and of the underlying periodic volume pattern.

Volume phase gratings have been fabricated by controlled generation of periodic striations during the growth of copper doped potassium lithium tantalate niobate crystals. Gratings with periods ranging from below 1 to 5μm were fabricated. It is shown that the fabricated composition grating induces a refractive index grating which is a superposition of a fixed grating and an electrically controlled (electrooptic) grating. The electrooptic grating is produced due to the generation of a spatial modulation of the Curie temperature which is manifested as a correlated modulation of the static dielectric constant. It was also observed that when operated at the immediate vicinity of the phase transition temperature the diffraction efficiency from these gratings was bi-stable at a specific electric field due to an induced shift of the Curie temperature.

A new approach to measure Curie temperature (T-C) of materials with phase transition in the range from -5 degrees C to + 70 degrees C is presented. In this work, measurements on potassium lithium tantalate niobate (KLTN) crystals are used to demonstrate the method. In this new approach the measurement is done directly over KLTN plates after cutting, without any additional processing. Contacts of conductive rubber are used as measurement points on the plates. Compared to traditional methods of T-C measurement, the presented method is faster, less expensive, non-destructive and easily enables the T-C topography on KLTN plates. The measurement set-up presented in this paper is fully automated and can measure T-C of 64 points on plates with area up to 40 mm x 40 mm with a resolution of 0.1 degrees C.

Non-volatile electroholographic diffraction gratings were fabricated by periodically modulating the composition of KLTN crystals. The gratings are manifested as periodic variations of the static dielectric constant which are electrically induced into birefringence gratings.

Undoped InP single crystals were grown by liquid-encapsulated Czochralski method (LEC) using glassy carbon, silica and PBN crucibles. The samples were characterized by Hall and resistivity measurements, photoluminescence at 2K and glow discharge mass spectroscopy. The residual impurity concentrations for InP grown using glassy carbon or silica crucible are of the same order of magnitude but both higher than that for InP grown with PBN crucibles. All samples exhibit good optical quality. The main acceptor impurities detected in all samples were C and Zn, while the main donors were S and Si. The InP grown from the glassy carbon crucible has the lowest C concentration and the main dopant detected in this sample was S originating from the crucible.