Showing papers by "Ganesan Ravi published in 2004"
TL;DR: In this paper, the crystal growth studies of 4-nitro-4′-methoxy benzylidene aniline (NMOBA) were reported, which was synthesized by condensation of the corresponding anilines and aldehyde.
28 citations
TL;DR: In this paper, near-stoichiometric LiNbO3 crystals with different compositions were grown by the top seeded solution growth method and the growth parameters such as temperature field, pulling, and rotation rates were optimized.
Abstract: Near-stoichiometric LiNbO3 crystals slightly doped with Mn from melts with different compositions are grown by the top seeded solution growth method. The growth parameters such as temperature field, pulling, and rotation rates are optimized. Two-color holograms are recorded in these crystals by the use of a near infrared laser of 778 nm for writing and an ultraviolet laser of 350 nm for gating. The light-induced absorption changes and two-color holographic characteristic performances are presented and compared. The results show that crystals with composition closer to stoichiometry exhibit better two-color holographic storage performance.
11 citations
TL;DR: In this article, single crystals of Rh-doped BaTiO3 have been grown by high-temperature solution growth technique, and the dopant level in the grown crystals was estimated by EDX analysis.
8 citations
TL;DR: In this article, Boric acid-mixed l- arginine phosphate monohydrate (LAP) has been synthesized with partial substitution of HF, HBr, CH 3 COOH and H 3 BO 3, and single crystals were grown successfully.
Abstract: New mixed compounds of l- arginine phosphate monohydrate (LAP) have been synthesized with the partial substitution of HF, HBr, CH 3 COOH and H 3 BO 3 , and single crystals were grown successfully. The addition of HF in LAP inhibits the microbial growth up to 40 days. Boric acid-mixed LAP is reported for the first time. The grown crystals were characterized by powder XRD, FTIR, UV–vis–NIR spectra. The preliminary work of powder SHG using Kurtz and Perry technique confirms the second harmonic generation effect in the grown crystals.
8 citations
TL;DR: In this paper, the photochromic process in LiNbO3 (LN) was shown to occur by an intervalence charge transfer between deep Mn2+/3+ and shallow Fe2+ /3+ energy levels.
Abstract: Stoichiometric LiNbO3 (LN) crystals doubly doped with Fe and Mn exhibited a strong reversible photochromic effect at room temperature. Irradiation with UV light induced a new absorption band extending from approximately λ=650 nm to the absorption edge, which could also be bleached by subsequent visible illumination. The dark decay times of induced absorption at room temperature were estimated to be approximately 2 months and more than a year for as-grown and oxidized crystals, respectively. Electron paramagnetic resonance analysis confirmed that the photochromic process in LN:Fe,Mn occurs by an intervalence charge transfer between deep Mn2+/3+ and shallow Fe2+/3+ energy levels. It was also found that only a small fraction of the doping ions are involved in the photochromic process.
3 citations
TL;DR: In this paper, the effect of Mn doping on two-color sensitivity and dynamic range (M/#) on gating and writing intensities are also investigated, and long dark storage time has been obtained for the doped crystal.
Abstract: Optical quality pure and Mn doped near stoichiometric lithium niobate (SLN) crystals were grown by top seeded solution growth using induction heating system. The growth parameters like temperature field, pulling and rotation rate have been optimized. Transmission studies revealed a shift in optical absorption towards longer wavelength for increased doping concentration. Curie temperature was found to decrease with Mn concentration. The effect of Mn doping on two-color sensitivity and dynamic range (M/#) on gating and writing intensities are also investigated. Long dark storage time has been obtained for the doped crystal.
3 citations
TL;DR: In this article, l -arginine fluoro phosphate was synthesized by adding 0.25 and 0.75 molar concentrations of HF and ortho phosphoric acids in l - arginine.
2 citations
TL;DR: The lifetime of holograms in lithium tantalate was 1 order of magnitude longer than that in lithium niobate with the same proton concentration, which was consistent with the theoretical estimation.
Abstract: Lifetimes of two-color nonvolatile holograms recorded in undoped or in slightly doped near-stoichiometric lithium niobate and tantalate crystals were measured and compared by extrapolation of the high-temperature data A proton-compensation mechanism dominated the dark decay and yielded similar activation energies, of 105 and 110 eV, for near-stoichiometric lithium niobate and tantalate crystals, respectively The lifetime of holograms in lithium tantalate was 1 order of magnitude longer than that in lithium niobate with the same proton concentration, which was consistent with our theoretical estimation The projected lifetime of two-color holograms in lithium tantalate without observable OH- absorption is longer than 50 years
1 citations
Proceedings Article•
16 May 2004
TL;DR: In this paper, light-induced absorption under illumination of continuous-wave ultraviolet laser in Mn-doped near-stoichiometric LiNbO/sub 3/ crystals was investigated for tailoring two-color nonvolatile holography.
Abstract: Light-induced absorption under illumination of continuous-wave ultraviolet laser in Mn-doped near-stoichiometric LiNbO/sub 3/ crystals was investigated for tailoring two-color nonvolatile holography. Dependences of probe wavelength, pumping intensity, crystal composition, and temperature on the light-induced absorption were presented.
22 Oct 2004
TL;DR: In this article, LiNbO 3 crystals slightly doped with Mn from different Li concentrations in the melt were grown by the top seeded solution growth method, and the light-induced small polarons absorption under UV illumination was probed using near-IR of 780 nm.
Abstract: Near-stoichiometric LiNbO 3 crystals slightly doped with Mn from different Li concentrations in the melt were grown by the top seeded solution growth method The light-induced (small polarons) absorption under UV illumination was probed using near-IR of 780 nm The dark decay process shows a stretched-exponential behavior The dependences of the light-induced absorption, the decay time constant, and the stretching factor on the pumping intensity were presented The photovoltaic current intensity and the photoconductivity under UV illumination were measured by applying a DC field along the z-axis of the sample The photoconductivity intensity showed superlinear dependence of intensity The experimental results can be explained quantitatively by developing the two-center charge transport model with direct excitation and recombination between Mn and small polarons