Wusheng Xu

Structure and Photo-Damage Resistance of Li-Rich LiNbO3 Crystals Co-Doped with Zn2+/Er3+

The pure congruent LiNbO 3 , Er:LiNbO 3 and Zn,Er co-doped Li-rich LiNbO 3 crystals were grown by Czochralski method. The X-ray diffraction method and ultraviolet-visible absorption spectra of the crystals were used to analyze the structure of the crystals. The photo-damage ability resistance of the crystals was measured. The Zn,Er co-doped Li-rich LiNbO 3 crystals show a decrease in lattice constant values, a shift in absorption edge of ultraviolet-visible absorption spectra towards shorter wavelength, and three orders of magnitude increase in photo-damage resistance compared to congruent LiNbO 3 crystal. The intrinsic and extrinsic defects are discussed to explain the enhance of the photo-damage ability resistance.

Effect of Li/Nb ratio on growth and photorefractive properties of Ce:Fe :LiNbO3 crystals

Zn:Fe:LiNbO3 crystals with different Li/Nb ratios in the melts (Li/Nb = 0.946, 0.97, 1.00, 1.10, 1.20, 1.44) have been grown for the first time. The UV–Vis absorption spectra, exponential gain coefficient, diffraction efficiency and response time of the crystals were measured. With the ratio of Li/Nb increasing, the absorption edge shifts to a shorter wavelength, the exponential gain coefficient and response speed increase, but the diffraction efficiency decreases.

Photorefractive properties of potassium lithium niobate doped with copper

Summary Potassium lithium niobate doped with copper (Cu:KLN) were grown by the Czochralski method for the first time. The structure of Cu:KLN was measured by the x-ray powder diffraction method, and its lattice constants were obtained. The position of copper ions in KLN crystal was determined. The exponential gain coefficient, response time and erasure time were measured. It was found that the exponential gain coefficient of Cu:KLN is 10.5 cm−1, as two times high as that of KLN, and its response time of 1.53 s is one order of magnitude shorter than that of Cu:LiNbO3. The type of light exciting carriers in Cu:KLN has been investigated. The result showed that the electron acts the main role in Cu:KLN.

Study on photodamage of Mg:Ga:LiNbO3 crystal wave-guide substrate

Abstract MgO and Ga 2 O 3 were doped in LiNbO 3 (LN) to grow Mg:Ga:LN crystals. The OH − absorption spectra and photoredamage resistance threshold of Mg:Ga:LN were measured. The mechanism of the shift of OH − absorption peak was investigated. LN crystal was manufactured into proton transfer wave-guide substrate. By using the holograph method, the photodamage resistance ability of wave-guide substrate was measured. It was found that the photodamage resistance ability of Mg:Ga:LN wave-guide substrate was much higher than that of LN wave-guide substrate.

Holographic storage property of In:Fe:LiNbO 3

In2O3 and Fe2O3 were doped in LiNbO3 and Czochralski method was used to grow In:Fe:LiNbO3 crystals. The light scattering ability resistance, exponential gain coefficient, diffraction efficiency and response time of the crystals were measured. The light scattering ability resistance and response time of In:Fe:LiNbO3 is one magnitude higher than Fe:LiNbO3. In:Fe:LiNbO3 was used as storage element to make the large capacity holographic storage and the holographic associative storage reality. The excellent results were gained.

Influence of post-growth treatment on the holographic storage properties of In:Fe:LiNbO3

Summary The congruent In (3 mol%):Fe (0.03 wt%): LiNbO3 crystal has been grown by Czochralski method in air. Some crystal samples were reduced in Li2CO3 powder, and others were oxidized in Nb2O5 powder. The defects and ions location in crystal were investigated by infrared (IR) transmission spectrum. The photorefractive properties were measured by two-wave coupling and light-induced scattering resistance experiments. In the oxidized sample, the photovoltaic effect was the dominant process during recording. However, for the as-grown sample as well as the reduced, the photorefractive effect was governed by the diffuse field and the photovoltaic field, together. In addition, the reduction treatment made the photoconductivity increase, which resulted in shorter erasure time and lower diffraction efficiency, but higher light-induced scattering resistance ability. The oxidation treatment caused the inverse effect.

First-order iteration associate storage of Ce:Eu:KNSBN crystal

Using Si-Mo Bar as the heater, potassium sodium barium strontium niobate (KNSBN) crystals doped with Ce and/or Eu have been grown by the Czochralski method. The exponential gain coefficients were measured by two-wave coupling light path, and in comparison with KNSBN, that of Ce:Eu:KNSBN is one time higher. Holographic associative storage principle is represented here and the holographic associative storage is realized by using Ce:Eu:KNSBN as the storage element and Mg:Fe:LiNbO3 as the phase conjugator to feedback, fetch threshold and gain. The output images are integrated.

Growth and holographic storage properties of Mg:Fe:LiTaO3 crystal

Mg:Fe:LiTaO3 crystals were first grown by Czochralski method, and Fe:LiTaO3 crystals, Fe:LiNbO3 and Mg:Fe:LiNbO3 crystals were also grown at the same time. The holographic storage properties of these crystals, such as the exponential gain coefficient, the diffraction efficiency and the response time, were measured by the two-wave coupling method. It was found that the response speed of Mg:Fe:LiTaO3 crystal was five times faster than that of Fe:LiTaO3. The light scattering resistance ability was also measured, and that of Mg:Fe:LiTaO3 crystal was two orders of magnitude higher than that of Fe:LiTaO3 as well as higher than that of Mg:Fe:LiNbO3. The enhancement mechanism of the photorefractive properties for Mg:Fe:LiTaO3 crystal was discussed for the first time.

Growth and holographic storage properties of MgLiNbO3 crystals

Mg(3mol%):Mn:Fe:LiNbO3 and Mg(7mol%):Mn:Fe:LiNbO3 crystals have been grown by doping 3mol%, 7mol% MgO in Mn:Fe:LiNbO3, respectively. It was found that light scattering resistance ability of Mg(7mol%):Mn:Fe:LiNbO3 is two orders of magnitude higher than that of Mn:Fe:LiNbO3 crystals. In Mg:Mn:Fe:LiNbO3 crystal, Mn is deep level and Fe is shallow level. We selected Mg(3mol%):Mn:Fe:LiNbO3 as the storage medium to carry the two-photon holographic storage experiment by using He-Ne laser as recording light and ultraviolet (UV) light as sensitizing light. The single photon recording and erasure curves as well as those of double photon were measured also. The recording speed of Mg:Mn:Fe:LiNbO3 crystals is faster than that of Mn:Fe:LiNbO3.

Growth and nonvolatile holographic storage properties of stoichiometric Eu:Fe:LINbO3 crystals

Congruent Eu:Fe:LiNbO3 crystals doped with or without fluxing agent K2O have been grown by TSSG method and the Czochralski method, respectively. The holographic storage properties, diffraction efficiency, response time and photoconduction, of the two Eu:Fe:LiNbO3 crystals are characterized by two-wave coupling experiment. Eu:Fe:LiNbO3 doped with fluxing agent K2O (Eu:Fe:SLN) has the higher photorefractive performances than congruent Eu:Fe:LiNbO3 (Eu:Fe:CLN). The nonvolatile holographic storage is realized in Eu:Fe:SLN crystals by using He-Ne laser as the light source and ultraviolet as the gating light.