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 152 cm^-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.