Haijun Qiao

Enhancement of ultraviolet photorefraction in highly magnesium-doped lithium niobate crystals.

We investigate UV photorefraction in Mg-doped LiNbO(3) crystals. Strong UV photorefraction is achieved in highly Mg-doped LiNbO(3) crystals with high two-wave mixing gain, fast response, and low noise. It is also demonstrated experimentally that so-called damage-resistant dopants such as Mg are damage resistant only in the visible and that they will enhance photorefraction in the UV.

An increase of photorefractive sensitivity in In:LiNbO3 crystal

The high sensitivity of photorefractive effect in indium doped lithium niobate was observed based on the two-wave mixing experiment. The sensitivity S was measured up to 2 cm 3 /J, even larger than the iron doped samples under the same configuration. The slightly indium doping seems to be an effective method to improve the photorefractive sensitivity of lithium niobate. 2002 Elsevier Science B.V. All rights reserved.

Enhanced second-harmonic generation by means of high-power confinement in a photovoltaic soliton-induced waveguide.

We present the first experimental demonstration of enhanced second-harmonic generation (SHG) by means of power confinement with a femtosecond laser in a photovoltaic soliton-induced waveguide. A dark spatial soliton created with a weak cw laser beam in a photovoltaic lithium niobate crystal induces an efficient waveguide for SHG, leading to a 60% enhancement of the conversion efficiency.

Observation of strong stimulated photorefractive scattering and self-pumped phase conjugation in LiNbO3:Mg in the ultraviolet.

We report on the observation of diffusion-dominant photorefraction and light-induced nonlinear forward and backward scattering in highly Mg-doped LiNbO3 at 351 nm. We also demonstrate what we believe to be the first continuous-wave self-pumped phase conjugation via stimulated photorefractive backscattering in the ultraviolet.

Ultraviolet-light-induced absorption changes in highly Zn-doped LiNbO3

Ultraviolet-light-induced absorption (UVLIA) in a highly Zn-doped LiNbO(3) crystal is studied at room temperature with various probe wavelengths from the violet to the near-infrared spectral regions. Transient dark buildup of UVLIA is observed in the violet-blue (<500 nm) region, while such a phenomenon is yet absent in the green-red (>500 nm) region. It is found that the temporal evolution of UVLIA in the dark is well described by a sum of two stretched exponential functions. These results are explained in terms of a three-level model involving two types of hole-trapped O- levels and one unintentional impurity FeLi level.

Fanning scattering in LiNbO3 at 750-850 nm induced by femtosecond laser pulses

We observed a light-induced fanning scattering in LiNbO3 at 750–850 nm, using femtosecond laser and without pumping. The fanning scattering is just like the ordinary one. After comparing the phenomena of some crystals, which were doped with different ions and one was oxided, and studying the threshold of the scattering, we think the scattering is owing to the small polarons formed by the self-gating of the bipolarons. 2003 Elsevier Science B.V. All rights reserved.

Light-induced backward scattering in LiNbO3:Fe,Zn

We investigated the light-induced backward scattering in doubly doped lithium niobate crystals and observed an intensity threshold effect. It will be shown that scattering microregions are locally recorded in the sample by holographic interaction due to the existence of the threshold effect. Experimental results of multilayer recording point out that this property could be used for high-density multilayer-like bit data optical storage while keeping high signal-to-noise ratio.

Simultaneous occurrence of beam deflection, holographic recording, and self-interference in one lithium niobate crystal.

Coupling of the acousto-optic effect and the photorefractive effect in a magnesium-doped lithium niobate crystal was studied by a holographic recording technique. The process of self-interference that is due to the coupling of these two effects was observed. Our results demonstrate that beam splitting and deflection, holographic recording, and self-interference can occur simultaneously in one crystal.

Ultraviolet-light-induced nonlinear scattering and self-pumped phase conjugation in LiNbO 3 :Mg crystals at 351 nm

We observe diffusion-dominant ultraviolet photorefraction and nonlinear scattering in highly Mg-doped LiNbO3at 351 nm. We also demonstrate self-pumped phase conjugation via nonlinear backward scattering in the ultraviolet for the first time.

OH- absorption spectra of the optical damage region in iron-doped lithium niobate crystals

We investigated the infrared spectra of the optical damage caused by laser diode at 808 nm in iron-doped lithium niobate crystals. The spectra show that the OH− absorption band in the region of the optical damage exhibits a structure consisting of three peaks. Comparing to the spectra at the non-damage region the main peak moves to red. The result will be helpful to microphotonic device applications.