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<011> -oriented TGS crystals have been irradiated by 100 MeV Ag7+ ions at different ion fluence. The crystalline samples thus irradiated by swift heavy ions (SHI) were subjected to various characterization tools such as HRXRD, optical absorption, dielectric, ferroelectric and piezoelectric measurements. AFM measurement was also used for studying the surface feature of samples upon irradiation. The results obtained for the irradiated samples from each measurement have been compared with the pristine ones. The collective results converge to the fact that irradiation-induced surface defects marginally influenced the bulk properties of the crystalline and it can be witnessed from the optical, dielectric and ferro-/piezoelectric behaviors of the crystal after irradiation. The other interesting results have been discussed in detail. [ABSTRACT FROM AUTHOR]

Single crystals of bismuth silicate (Bi12SiO20) doped with chromium (0.05, 0.25, 0.5, and 1.0 at%) have been grown along ⟨110⟩ by Czochralski technique. The effect of growth parameters like low axial thermal gradient and crystal rotation rate on the crystal−melt interface is investigated by varying these parameters. Further, the effect of Cr incorporation on the lattice parameter, optical bandgap, emission characteristics, and refractive index is studied. It is observed that as the concentration of Cr increases, the lattice parameter increases, because the size of Cr ion is higher than that of Si ion which it replaces. The bandgap is found to decrease with the increase in the concentration of Cr in the lattice of Bi12SiO20. The estimated bandgap energy of all the samples lies between 2.16 and 3.12 eV. The estimated Urbach energy is ≈115 meV for undoped BSO and it is slightly higher (≈200 meV) for Cr‐doped crystals. Further, 0.05 and 0.25 at% Cr‐doped samples exhibit emission peak at around 470 nm on excitation at 420 nm. The refractive index is found to decrease with the increase in Cr concentration in the lattice. [ABSTRACT FROM AUTHOR]

Bulk size pyroelectric undoped and Cd- and Mn-doped lithium sulfate monohydrate (LSMH) single crystals were successfully grown along the polar axis by the unidirectional crystal growth method. The influence of transition metal ions (Cd and Mn) on crystal growth and the linear/nonlinear optical, pyroelectric, and piezoelectric properties of the LSMH crystal were studied. The crystalline perfection of the grown crystals was assessed using a rocking curve of the HRXRD pattern. The vibrational spectroscopic properties of undoped and doped single crystals were analyzed using micro-Raman scattering measurements on the 〈010〉-oriented crystal surface. The optical quality was assessed by recording the UV-Vis-NIR transmission on the different sectors of the crystal. The refractive index at five different wavelengths in the range of 407–1551 nm and birefringence properties of Cd- and Mn-doped crystals were analyzed using the prism coupling method. The second harmonic generation capability of the material was studied using the Kurtz and Perry technique. The pyroelectric coefficients of these crystals were determined by measuring the pyroelectric current as a function of temperature. Piezoelectric studies were carried out on the (010) surface of the undoped and doped samples. The LSMH crystals grown from a solution containing Mn ions were found to have a satisfactory second harmonic generation capability and piezoelectric coefficient. [ABSTRACT FROM AUTHOR]

$$\upalpha $$ - $$\hbox {LiIO}_{3}$$ is an excellent optical material exhibiting strong nonlinear optical, piezoelectric and elasto-optic properties. However, its practical applications are limited by the insufficient reproducibility of the mentioned properties caused by the strong influence of the growth conditions, and, in particular, pH of the solution from which $$\upalpha $$ - $$\hbox {LiIO}_{3}$$ crystal is grown. Herein, we investigate to grow bulk size good quality crystals of $$\upalpha $$ - $$\hbox {LiIO}_{3}$$ based on the observed problems during its crystallization process. A systematic investigation was carried out to find the effect of pH on solubility, crystal growth, structural, surface and laser damage properties of $$\upalpha $$ - $$\hbox {LiIO}_{3}$$ single crystals. The structure and phase of $$\hbox {LiIO}_{3}$$ were confirmed by powder X-ray diffractometer analysis. The functional groups of the compound were identified using Fourier transform infrared spectroscopy. Surface defects of the grown crystals were studied by etch patterns. The crystal grown at pH 10 showed 10% optical transmission enhancement in comparison to the crystals grown at pH 2. The indirect optical bandgap of the crystal was reinvestigated using ultraviolet-Visible-near-infrared transmittance spectrum. The laser damage threshold studies of the crystals grown at pH 10 reveal the higher optical radiation stability against 532 nm laser. The second-order nonlinear optical behaviour of $$\upalpha $$ - $$\hbox {LiIO}_{3}$$ crystals grown at different pH conditions have been investigated by using Kurtz and Perry powder technique with Nd:YAG laser pulses at the wavelength of 1064 nm. [ABSTRACT FROM AUTHOR]

A single crystal of lithium niobate is an important optoelectronic material. It can be grown from direct melt only in a lithium deficient non-stoichiometric form as its stoichiometric composition exhibits incongruent melting. As a result it contains a number of intrinsic point defects such as Li-vacancies, Nb antisites, oxygen vacancies, as well as different types of polarons and bipolarons. All these defects adversely influence its optical and ferroelectric properties and pose a deterrent to the effective use of this material. Hence, controlling the defects in lithium niobate has been an exciting topic of research and development over the years. In this article we discuss the different methods of controlling the intrinsic defects in lithium niobate and a comparison of the effect of these methods on the crystalline quality, stoichiometry, optical absorption in the UV-vis region, electronic band-gap, and refractive index. [ABSTRACT FROM AUTHOR]

Abstract: Vapour transport equilibrium (VTE) technique was used to prepare near stoichiometric LiNbO3 (NSLN) crystals. Simultaneous occurrence of reduction has been observed during the Li-enrichment that results in the weak absorption bands centred at 1.7, 2.6 and 3.7eV in the absorption spectrum. Annealing in oxygen atmosphere resulted in decrease in the intensity of these bands. The indirect and direct band-gap energies for NSLN crystals evaluated from absorption studies are reported. The energy of the phonon involved in the indirect transition is ∼85meV (685cm−1). Near room temperature ac-conductivity measurements reveal lower conductivity for oxygen annealed NSLN crystal in comparison to as prepared NSLN and CLN specimens. The activation energies for ac-conductivity along the z-direction for NSLN and CLN crystals in the temperature range 500–1100K are 1.03eV and 0.96eV, respectively. [Copyright &y& Elsevier]

Abstract: Beta barium borate (β-BaB2O4; BBO) single crystals have been grown from Na2O flux by the TSSG technique and the observed growth rate anisotropy is reported. The symmetrical conoscopic interference pattern on the c-cut plate confirmed strain-free and optical homogeneity of the crystals. The observed growth habits of as-grown crystals are explained using crystal growth theories. The relative growth rate along different crystallographic directions of BBO can be described by R [100] = R [010] > R [001]. The absorption measurements show a nearly 9nm shift in fundamental absorption edges in X and Z cut samples. Band gap energies measured were 6.45 and 6.2eV along the X and Z directions, respectively. The absorption spectra near the fundamental absorption edges (AE) follow Urbach’s rule. [Copyright &y& Elsevier]

Undoped and MgO doped LiNbO 3 crystals were grown by Czochralski technique. Blue shift in absorption edge was observed with MgO doping. The nonlinear optical properties of undoped and doped crystals were measured experimentally using Kurtz powder SHG analysis. According to defect structure model, the relative SHG efficiency is critically MgO doping and Li/Nb ratio dependant. The NLO coefficient were observed 40 times higher than KDP for undoped and 3 mol.% MgO doped crystals. [ABSTRACT FROM AUTHOR]

Optical and photoluminescence studies on Cr doped LiNbO3 single crystals have been carried out. Three different Cr doped compositions, with 0.1, 0.25 and 0.5 mol% Cr2O3, of congruently melting LiNbO3 single crystals were grown by the Czochralski technique. Optical transmission studies showed prominent absorption bands in the visible region of the spectrum at photon energies of 1.9 and 2.57 eV. A significant red-shift of 60 nm was observed in the UV absorption edges of doped crystals. This can be explained in terms of the overall decrease in the Li/Nb ratio in the doped crystals, caused by extrinsic defects generated by the Cr3+ impurity. The absorption coefficient of the material increases significantly with Cr doping concentration. The band gap decreases with increasing Cr concentration. The excitation-independent broadband luminescence was observed in the spectral range of 700–1100 nm, with a peak around 900 nm in the photoluminescence (PL) studies. The broadband PL emission makes the material a potential candidate for diode pumped all solid-state tunable laser. [Copyright &y& Elsevier]

A method is described for growing inclusion-free crystals of KTP using 〈0 1 0〉 seed orientation. The top seeded solution growth technique is employed, along with a high rotation rate for the seed crystal, using a five-zone resistive-heating furnace. A minimum wastage of the seed is achieved by maintaining the seed–liquid interface by surface tension forces. Elements fabricated from KTP crystals under Type II phase matching for second-harmonic generation from Nd:YAG radiation exhibited a conversion efficiency exceeding 60% (without anti-reflection coating). [Copyright &y& Elsevier]