LiNbO3 Single Crystal Fibers Research Articles

Optical properties of thea-axis lithium niobate single-crystal fiber with applied electric field

The optical properties of the a-axis lithium niobate (LiNbO3) single-crystal fiber are theoretically studied in this paper. We solve the electromagnetic field equations of the anisotropic a-axis single-crystal fiber and numerically analyze the mode characteristics of the a-axis LiNbO3 single-crystal fiber which only conducts the second-order elementary mode. We discuss the effect of the applied electric field on the refractive index anisotropy and the mode characteristics of this type of fiber which only conducts the second order elementary mode.

Electric field modulated specklegram phase multiplexing technique for volume holographic

We report a speckle-based hologram multiplexing recording technique, in which a multimode LiNbO3 single crystal fiber is employed to generate speckle patterns of reference beams in hologram recording process. By applying an external E-field, the speckle pattern generation and reconstruction can be precisely controlled. A theoretical analysis and a numerical simulation of speckle pattern generation have been conducted. According to the simulation results, this technique can generate thousands of decorrelated reference beams at given practical constraints. The storage capacity can be scaled up as material properties are improved, making this technique well adapted to new material development.

Growth and optical properties of different compositions of LiNbO3 single crystal fibers

In this study the laser-heated pedestal growth (LHPG) method was used to grow lithium niobate (LiNbO3) single crystal fibers. The composition ratio were: [Li2CO3]/[Nb2O5]=44:56, 45:55, 46:54, 47:53, 48:52, 48.6:51.4, 49:51 and 50:50 and were achieved by using different seed rods. The lattice parameters and crystalline structure of the crystals were determined by X-ray Single-Crystal Diffractometer (X-ray/CCD). The UV absorption spectra, Fourier-transform infrared spectrometer and Raman scattering spectroscopy results were used to find the optical properties and standard characterization of the different LiNbO3 single crystals. We note that the wavelength of the UV absorption edge was less when the Li2O composition was large. The plotted results, with the exception of the stoichiometric lithium niobate results, tended to fit a 2nd order polynomial curve. Transformation of the O–H absorption bands was observed. The Full-Width Half-Maximum (FWHM) of the Raman peak was found at 152cm−1 in the E(TO) mode and decreased linearly as the amount of the Li2O composition increased. The Raman scattering results confirmed that the structure of the LiNbO3 crystals became more rigid when the amount of the Li2O composition increased.

Characterization of iron substitution process in Fe:LiNbO3 single crystal fibers by polaron measurements

Abstract The growth of iron-doped single-crystal fibers of lithium niobate was performed by the Laser Heated Pedestal Growth Technique for different Fe 2 O 3 contents in the feed rods. We used the polaron luminescence to explain the processes of iron substitution in iron-doped single-crystal fibers of lithium niobate. The interpretation of the polaron behavior as a function of iron concentration confirms several predicted effects as the decrease of the global amount of vacancies and the predominant role of the niobium in its polaronic or bipolaronic forms in the LN lattice.

Influence of the dopant concentration on the OH− absorption band in Fe-doped LiNbO3 single-crystal fibers

Abstract The growth of iron-doped single-crystal fibers of lithium niobate was performed by the laser heated pedestal growth technique for different Fe2O3 contents in the feed rods. The infra-red optical absorption spectra (OH− band) were investigated by IR transmission microscopy. To explain the evolution of the OH− ions concentration in the crystals, a model is proposed involving the partial dissociation of LiNbO3 in the melt into Li2O and Nb2O5. The constitution of the OH− absorption band is also discussed on the basis of the Nb-vacancy structural model of lithium niobate.

Micro-Pulling Down Growth of Co-doped Lithium Niobate Single Crystal Fibers According Er and Mg Contents and Photolumenescence Properties

The Er3+doped Mg:LiNbO3single crystal fibers employed in our experiment were grown in air by a micro-pulling down (μ-PD) method from host materials of a congruent Li/Nb (0.945) ratio which were melt-doped with a nominal molar concentration of 1, 3, 5% MgO and 0.6% Er2O3. The X-ray diffraction analysis results indicated that the co-doped crystals main tained the same structural characteristics as the undoped LiNbO3, however the lattice parameters with Mg differed; c (Å) value decreased, and a (Å) increased than of pure LiNbO3. The influence of dopants on the photoluminescence (PL) properties of the Er:Mg:LiNbO3 single crystal fibers excited by laser lines of 514 nm was reported. Also, the PL properties according to temperature and the excitation power of Er:Mg:LiNbO3 crystal fibers were analyzed.

Second-harmonic generation using an <italic>a</italic> axis <inline-formula><roman>Nd:MgO:LiNbO</roman><sub><roman>3</roman></sub></inline-formula> single crystal fiber with Mg-ion indiffused cladding

We report the implementation of a low-loss core-cladding waveguide structure of an a axis Nd:MgO:LiNbO3 single-crystal fiber with a step refractive index profile and the demonstration of a frequency- doubled laser made from such a cladded crystal fiber. The laser-heated pedestal-grown a axis single-crystal fiber, with an elliptical crosssectional area of 200x 150?m, is further shown with a Mg ion indiffusion process. Electron probe microanalysis is used to measure the Mg ion concentration distribution in the Mg-diffused layer. After several trials, diffusion parameters suitable for achieving a core-cladding waveguide structure with a step refractive index profile are obtained. The optical and structural properties of the cladded crystal fibers are also characterized. Room-temperature second-harmonic generation with such a cladded crystal fiber is demonstrated. At room temperature, cw green laser output with a power of 10 ?W at the wavelength of 0.532 ?m is achieved. The origin of the relatively low conversion efficiency is discussed.

Magnesium-Ion Indiffusion to Lithium Niobate Single-Crystal Fiber with MgF2 as Diffusion Source

A study of the Mg-ion indiffusion to lithium niobate (LiNbO3) single-crystal fiber was carried out using MgF2 as the diffusion source. A core-cladding waveguide structure was obtained for a c-axis LiNbO3 single-crystal fiber with a diameter of 200 µm, and the optical characteristics of the cladded crystal fiber were given. By means of electron probe microanalysis, the activation energy for Mg-ion indiffusion was estimated to be 104 kJ/mol. It was also found by X-ray diffraction analysis that the Mg-diffused layer has serious lattice distortion and the LiNb3O8 compound appears beyond a certain extent of Mg-ion indiffusion. The appearance of the LiNb3O8 compound is related to Li-ion outdiffusion from the bulk of LiNbO3 and the large amount of F ions from MgF2 due to Mg-ion indiffusion to LiNbO3. It was indicated by scanning electron microscopy that F ions appear in the form of LiF particles and these particles volatilize from the surface of the Mg-diffused layer with increased diffusion.

Second-harmonic generation in a microradius LiNbO_3 cylinder with a quasi-elliptical cross section

LiNbO(3) single-crystal fibers with diameters of 63 and 230 mum were grown, and the second-harmonic-generation (SHG) process was studied with femtosecond laser pulses perpendicularly focused to the fiber. SHG occurred without collinear phase matching, leading to wavelength-independent overall conversion efficiency, unlike in a bulk crystal. The scattering pattern of the second harmonic exhibited an intense forward peak and an almost-uniform, less-intense distribution around the fiber, owing to trapping in high-Q whispering modes. Implementation of a second-order autocorrelator with the 63-mum fiber demonstrates its application potential.

A-Axis Nd:MgO:LiNbO3 single crystal fibers with magnesium-ion indiffused cladding

A core-cladding waveguide structure for the a-axis Nd:MgO: LiNbO3 single crystal fiber with parabolic refractive index profiles was achieved by a Mg-ion indiffusion process. Propagation loss coefficient of the cladded crystal fiber was measured and is 7 times lower than the uncladded crystal fibers. Transmission modes of the 60μmlm × 45μmlm cladded crystal fiber were observed and the low order modes propagation was obtained

Growth of MgO doped LiNbO3 single crystal fibers by a novel drawing down method

MgO-doped LN (LiNbO3) fibers were automatically grown by an improved drawing down method. The smallest fiber diameter ever attained was 10 μm and the fluctuation in diameter was reduced to ±0.2 μm. The poling process was done during the growth process by the thermal electric effect. The dislocation which was observed in the X-ray topographs of the optical grade bulk crystals did not appear in the fiber. The fibers and optical grade bulk crystals did not have a uniform distribution of the MgO concentration as determined by electron probe micro analysis (EPMA).

Uniform refractive index cladding for LiNbO3 single-crystal fibers

A uniform refractive index cladding for LiNbO3 single-crystal fibers has been achieved using a Mg ion indiffusion process. This cladding has a uniform MgO concentration of ∼20 mol %, resulting in a uniform refractive index. The refractive indices of the cladding material have been evaluated to be ne=2.08 and no=2.09 at 0.6328 μm by using the light reflection technique.

Ferroelectric domain structures in LiNbO3 single-crystal fibers

The ferroelectric domain structures of small diameter LiNbO3 single crystal fibers were found to be different from those usually observed in large LiNbO3 crystals. c-Axis grown fibers with diameters up to 800 μm were found to be virtually single domain with +c end facing the melt during growth. Fibers grown along the a-axis had a bi-domain configuration with the domain boundary along the a-axis and parallel to the c-face. A model is proposed, based on the thermoelectric potential generated by axial and radial temperature gradients, to explain the domain structures observed in these fibers.