Crystal growth of Ru-doped congruent LiNbO₃and investigation of crystalline perfection and optical properties

Abstract

Single crystals of undoped and Ru-doped congruent LiNbO 3 (LN) were successfully grown by the Czochralski method. The axial and radial gradient of the radio frequency furnace was controlled in order to obtain crack-free single crystals. Wafers were cut from the grown Ru-doped single crystal at different axial positions along the growth direction and subjected to various characterization analyses. Good optical homogeneity and low residual strain in the grown crystal is confirmed by the conoscopy patterns. Further, it is confirmed that Ru doping does not influence the optical sign of the crystal. From a high-resolution X-ray diffractometry analysis, it is evident that the as-grown undoped LN crystal exhibited better crystalline perfection with a single and sharp diffraction curve in comparison to the Ru-doped crystals, which are characterized by a broader diffraction curve. Absorption coefficient and band-gap analysis across the axial length revealed a concentration variation of Ru across the length. Refractive index measurements carried out using a prism coupler showed variation in the optical birefringence, also due to the variation of Ru concentration at different positions of the grown single crystal.

Nanoindentation and structural studies of MgO-doped congruent LiNbO3 single crystals

“…More details of the crystal growth have been reported previously in ref. 39. In our earlier study of HRXRD on these Mg:LN single crystal sample it has been reported that the FWHM of the diffraction peak is ~ 29-112 arc sec signifying the good crystalline quality of the grown crystal [39].…”

“…LN is ferroelectric at room temperature with the R3c space group. Single crystals of LN can be grown from stoichiometric composition (SLN), with the Li/Nb molar ratio of 50:50 as well as from the congruent composition (CLN) with the Li/Nb ratio of 48.6:51.4 [7,8]. It has been well established that many of the physical properties of LN crystals depend on the composition.…”

Investigations on Crystalline Perfection, Raman Spectra and Optical Characteristics of Transition Metal (Ru) Co-Doped Mg:LiNbO3 Single Crystals

“…Due to the closeness of Ru with Fe, it is assumed that the doping effect of Ru in nonlinear crystals would be similar. The Ru-ion doping in NLO crystals has been studied, such as in Ru:LiNbO 3 , 28 Ru:Bi 12 SiO 20 , 27 Ru:Bi 4 Ge 3 O 12 , 29 Ru:Sr 0.61 Ba 0.39 Nb 2 O 6 , 30 and Ru:Bi 12 TiO 20 . 31 Like Fe, Ru-ion doping in LN may be supportive to improve the photorefractive characteristics.…”