Xu Yuheng

OH− absorption and nonvolatile holographic storage properties in Mg:Ru:Fe:LiNbO3 crystal as a function of Mg concentration

Mg:Ru:Fe:LiNbO3 crystals with various concentrations of MgO (in mole) and fixed content of RuO2 and Fe2O3 (in mass) are grown with the Czochralski method from the congruent melt. Their infrared transmission spectra are measured and discussed to investigate the defect structure. With the increase of Mg2+ concentration the blue nonvolatile holographic storage capability is enhanced. The nonvolatile holographic storage properties of dual-wavelength recording of Mg(7 mol%):Ru:Fe:LiNbO3 nonvolatile diffraction efficiency, response time, and nonvolatile sensitivity reach 59.8%, 70 s, and 1.04 cm/J, respectively. Comparing Mg(7 mol%):Ru:Fe:LiNbO3 with Ru:Fe:LiNbO3 crystal, the response time is shortened apparently. The nonvolatile diffraction efficiency and sensitivity are raised largely. The mechanism in blue photorefractive nonvolatile holographic storage is discussed.

Influences of Mg2+ ion on dopant occupancy and upconversion luminescence of Ho3+ ion in LiNbO3 crystal

The effects of a Mg2+ ion on the dopant occupancy and upconversion luminescence of a Ho3+ ion in LiNbO3 crystal are reported. The birefringence gradient of the crystal is measured to investigate the optical homogeneity. The X-ray powder diffraction spectrum and the upconversion luminescence are used to investigate defect structure and spectroscopic properties of Mg,Ho:LiNbO3. Under 808-nm excitation, blue, red, and very intense yellow-green bands are observed. Based on the energy levels of Ho3+ in LiNbO3, and the pump intensity dependence of the observed emission, an excitation scheme is presented. The upconversion emission spectra reveal an enhancement of upconversion intensity when the Mg2+ ions are introduced into Ho:LiNbO3. The main upconversion mechanism is discussed in this work.

Anomalies of Doped-LiNbO3 Crystal in Photorefractive Phase Conjugation with Relation to Structural Phase Transformation

We investigate the photorefractive phase conjugation in a Ce:Fe:LiNbO3 crystal as a function of temperature (293-393 K) and find the phase conjugate reflectivity increases sharply in the vicinity of 55, 70 and 110° C. The anomalous phenomenon is possibly concerned with the structural phase transformation of a crystal, which induces an extra internal electric field to influence the phase conjugation. The value of the field is estimated at the order of 105 V/m, in agreement with the published data.

Very High Photorefractive Gain in Two-Beam Coupling with Thin Iron-Doped LiNbO3 Crystal

The largest exponential gain coefficient (Γ = 250 cm-1), to our knowledge, is obtained in thin (d = 0.20 mm) iron-doped LiNbO3 crystal. The dependence of two-beam coupling coefficients on beam crossing angle are measured and compared in two samples fabricated from the same material with different values of thickness. The explanation based on light climbing effect is given.

Photorefractive effect of double doped Ce:Co:KNSBN crystal

Abstract The Ce:Co:KNSBN crystal was grown for the first time by means of Czochalski technique. The Crystal has a higher exponential gain coefficient, the diffraction efficiency, the phase conjugate reflectivity and self-pumped phase conjugate reflectivity than the undoped KNSBN crystal. The simple iterative holographic storage was realized by using a Ce:Co:KNSBN crystal as a storage device and a Zn:Fe:LiNbO3 crystal as photorefractive crystal amplifier, respectively.

Light-Induced Absorption in Nominally Pure Bismuth Silicon Oxide

Light-induced absorption in the nominally pure bismuth silicon oxide is investigated experimentally and the result shows that it consists of transient and persistent parts. The experimental evidence is analysed based on the model of three groups of trap (donor) centres.