Structural redetermination, thermal expansion and refractive indices of KLu(WO₄)₂

Abstract

The crystal structure of monoclinic KLu(WO 4 ) 2 (KLuW) crystals was determined at room temperature by using single-crystal X-ray diffraction data. The unit-cell parameters were a = 10.576 (7), b = 10.214 (7), c = 7.487 (2) Å , = 130.68 (4) , with Z = 4, in space group C2/c. The unit-cell parameters of KLu 1Àx Yb x (WO 4 ) 2 were determined in relation to Yb concentration. Vickers micro-indentations were used to study the microhardness of KLuW. The linear thermal expansion tensor was determined and the principal axis with maximum thermal expansion ( 0 33 = 16.72 Â 10 À6 K À1 ), X 0 3 , was located 13.51 from the c axis. The room-temperature optical tensor was studied in the near-infrared (NIR) and visible range. The principal optical axis with maximum refractive index (n g = 2.113), N g , was located 18.5 from the c axis at 632.8 nm. Undoped and ytterbium-doped KLuW crystals were grown by the TSSG (top-seeded-solution growth) slow-cooling method. The crystals show {110}, { " 1 111}, {010} and {310} faces that basically constitue the habit of the KLuW crystals.

Thulium doped monoclinic KLu(WO4)2 single crystals: growth and spectroscopy

“…Applied Physics B -Lasers and Optics FIGURE 6 RT polarized absorption crosssections of Tm 3+ in KLuW single crystal [24], refractive index using the Sellmeier values of KLuW [2] and the accuracy of the J-O parameters is given by the goodness of the least-squares fitting used, root mean square value (rms); also indicated in Table 4. Also magnetic dipolar (MD) contributions to the experimental oscillator strengths was taken into account to calculate the electrical dipole (ED) contribution, f ED,exp .…”

“…The feasibility of growing highly doped ytterbium KLuW material [2] and the excellent results of its ytterbium laser action [3]; are good enough reasons for growing Tm:KLuW single crystals and studying thulium spectroscopy in KLuW.…”

“…The sample was a parallelepipedic prism with the faces parallel to a principal optical plane (N g -N m plane, N g -N p plane and N m -N p plane) so that polarized measurements could be taken. The location of the principal optical axis and optic axes in KLuW is described elsewhere [2].…”

“…• [2]. Because this material is important as a host for lanthanide doping, the measurement of the change in the unit cell parameters is useful for predicting the structural changes related to the doping and the mismatch for epitaxial film growth [14].…”

Potassium double tungstate waveguides with high ytterbium concentration for optical amplification

“…Therefore, it is used more often for amplifiers and lasers in comparison to both Ng and Np axes. The dispersion curves at Nm for KGd(WO4)2 [113], KLu(WO4)2 [112], KY(WO4)2 [103], and KYb(WO4)2 [104] are depicted in Figure 3.3(b). Among these double tungstate crystals, the KY(WO4)2 exhibits the lowest refractive index value while the KYb(WO4)2 has the highest value, with two of them differ by ~0.029 at 1000 nm wavelength.…”