KLN Crystals Research Articles

Second harmonic generation of ferroelectric potassium lithium niobate crystals

Potassium lithium niobate (KLN) crystals with various Li2O compositions have been grown by a resistance-heating Czochralski technique. The solid-liquids interfaces for the steady crystal growth, as well the cracking mechanisms were investigated. The optical transmittance spectrum showed that the KLN crystal with higher Li2O content presents higher transmission than that with lower Li2O content. Moreover, the second harmonic generation (SHG) signal can only be distinguished for the crystal with high Li2O concentration. The properties of doubling near infrared cw Ti:sapphire laser in the wavelength range of 820–960 nm have been demonstrated for the KLN crystal with Li2O 26 mol% and Nb2O544 mol%.

Czochralski Growth of Potassium Lithium Niobate Single Crystals with Low Li Content and Their Characterization

Single crystalline and crack free potassium lithium niobate (KLN) single crystals with low Li content were grown by the Czochralski method. The crystal composition can be written as K 2.60 Li 1.17 Nb 5.44 O 15 (=K 2.95 Li 1.33 Nb 6.17 O 17 ) which contain relatively fewer Li ions than ferroelectric K 3 Li 2 Nb 5 O 15 crystals. All experimental results show that the deficiency of the Li ions in the KLN crystals strongly influences their physical properties. Especially, the as-grown crystals do not indicate any signature for a ferroelectric phase transition in contrast to the ferroelectric K 3 Li 2 Nb 5 O 15 crystals. However, due to ionic conduction, the temperature dependence of the dielectric constant of such KLN-2 crystals show a broad anomaly near 300°C. In addition, the existence of proton defects can be revealed by infrared absorption spectroscopy near 3500 cm -1 in as-grown crystals.

Diffuse Phase Transition in Potassium Lithium Niobate Ferroelectric Crystals

The tungsten-bronze type ferroelectric potassium lithium niobate (KLN) crystals were grown by the Czochralski technique. In order to obtain a crystal with high quality and crack free, crystal growth is performed in two orientations along c and a -axis. We have subjected these crystal to X-ray diffraction studies and found that they are single-crystalline and belong to the tetragonal system with the lattice constants a = b = 1.2500 nm and c =0.3996 nm. The spontaneous polarization, DSC and dielectric constant were measured in the temperature range between 30°C and 700°C. The diffuse dielectric anomaly was observed for these KLN crystals. The phase transition temperature and diffuseness of phase transition are different at several crystals. These behaviors are explained by DPT, it means that the compositional fluctuation and cation distribution has a strong influence on the ferroelectric properties. Diffuse phase transition establishing the influence of composition on structure and dielectric properties are...

Growth and Structure of Doped KLN Crystal

KLN, Fe:KLN, Mn:KLN and Cu:KLN crystals were grown by Czochraski method. The structure of crystal was measured by X-ray diffraction technique. The results indicated that the doped crystals kept the same structural characteristics as the pure KLN crystal, but the lattice constants of Fe:KLN and Mn:KLN crystals became smaller than that of pure KLN crystal, and that values of Cu:KLN crystal became larger than that of pure KLN crystal. This indicated that Fe and Mn cations replaced Nb cation, and Cu cation replace K cation after they entered into the lattice of KLN crystal. The result of ultraviolet-visible absorption spectra was identified with that of X-ray diffraction analysis.

Studies on the growth and properties of magnesium-doped potassium lithium niobate single crystal

Magnesium-doped potassium lithium niobate (designated as Mg:KLN) single crystal free of cracks was grown for the first time. The tetragonal tungsten bronze structure of the Mg:KLN crystal was determined by X-ray powder diffraction; the lattice parameters were a = 1.261 and c = 0.398 nm. High-temperature X-ray powder diffraction patterns show that the expansion of the lattice with increasing temperature was less than that of the undoped crystal. The transmittance of the as-grown Mg:KLN crystal was measured. It only took 70 nm for the transmittance to increase to 70% from the cutoff of 380 nm. The transmittance for 404 nm was 50%, which was greater than that for the undoped crystal. Frequency-doubling experiment showed that the crystal generated blue light at a wavelength of 404 nm through noncritical phase matching frequency-doubling of an 808 nm diode laser at room temperature.

Growth of potassium lithium niobate (KLN) single crystals for second harmonic generation (SHG) application

We have grown potassium lithium niobate (KLN) single crystals by TSSG method using different melt compositions as follows: K 2O in the range of 30.5–34%, Li 2O in the range of 26.5–22% and Nb 2O 5 in the range of 43–45%. The composition of KLN crystals varied sensitively with the change of Nb content in the Li- and K-rich melts. The KLN crystals exhibit a good compositional homogeneity, high optical transparency and excellent SHG properties. Their non-critical SHG phase matching wavelengths were in a wide range of between 840 and 970 nm corresponding to the change of Nb content of crystals being less than 3 mol%.

Morphology of TSSG grown potassium lithium niobate (KLN) crystal in relation to its structure and growth conditions

The growth form and the crystal–melt interface of KLN crystals grown along 〈0 0 1〉, 〈1 0 0〉 and 〈1 1 0〉 directions by the TSSG method have been studied in detail. The well-developed facets have been unambiguously indexed by using XRD and stereographic projection analysis. The crystal structure and cell parameters were determined and calculated on the basis of XRD data. The order in morphological importance (MI) of KLN crystals was predicted by the BFDH law and compared with our experimental results. The growth mechanism and defects of KLN were discussed according to the facet morphology on the crystal–melt interface.

Bridgman growth and properties of potassium lithium niobate single crystals

Transparent KLN crystals 10mm in diameter and 25 to 45mm in length have been grown by the modified vertical Bridgman technique from different melts in the range of 30∼35mol% K 2O, 17∼23mol% Li 2O and 43∼50mol% Nb 2O 5. The growth conditions are a growth rate of less than 0.25 mm/hr, temperature gradient in solid-liquid interface of 2∼3 °C/mm and growth direction of <110>. As-grown KLN crystals have tetragonal tungsten bronze structure. Most of the as-grown crystals do not crack when cooling through the paraelectric/ferroelectric phase transition. 180° domain structures are observed after the KLN crystal was etched in boiling 2HNO 3:Hf. Dielectric properties and transmission spectrum of the as-grown KLN crystals are measured.

Magnesium-doped potassium lithium niobate crystal and its properties

High quality magnesium-doped potassium lithium niobate (designated as KLN:Mg) single crystal was grown for the first time. The tetragonal tungsten bronze structure of the Mg:KLN crystal was determined by X-ray powder diffraction, in which the lattice parameters were a=1.262nm and c=0.398nm. High temperature X-ray diffraction patterns showed that the expansion of the lattice with increasing temperature was less than that of the undoped crystal. The transmittance of the as-grown crystal was measured. It increased by 80% from the cutoff wavelength 380nm to 450nm. The transmittance for 404nm was 50%, which is larger than that of the undoped crystals. The frequency-doubling property of KLN crystal was analyzed. Preliminary frequency doubling experiments showed that the crystal could generate blue light of 404nm through noncritical phase matching (NCPM) second harmonic generation (SHG) using a 808nm diode laser at room temperature.

Growth and properties of potassium lithium niobate (KLN) single crystals

KLN crystals with good quality and size up to 15 χ 20 χ 25 mm3 have been grown from different melt compositions by top seeded solution growth (TSSG) method. The composition of crystals varies with the change of melt composition, especially the content of niobium in the melt. The KLN crystals exhibit a high second-harmonic generation efficiency (∼20 %), a wide wavelength acceptance (∼1.5 nm) and a temperature acceptance (∼4°C) one order higher as compared with KNbO3 crystals. The phase matching wavelength increases with increasing the ratio of niobium to lithium in the crystal.

Top seeded solution growth and characterisation of ferroelectric potassium lithium niobate crystals

We have grown KLN crystals from different melts by the TSSG method at our laboratory. The melting and crystallisation behaviours of the raw materials have been studied by the DTA method. The crystal compositions were measured by chemical analysis and the solute segregation effects between the melt and crystal were discussed. The crystal structure and optical properties were characterised by means of XRD and optical spectrum measurement. The blue SHG effect of the as-grown crystals was also examined by a dye laser.

Potassium lithium niobate: single-phase domain boundary in the 30 mol% K 2O isopleth of the ternary system Li 2O–K 2O–Nb 2O 5 and characterization of single-crystal fibers

K 3Li 2−xNb 5+xO 15+2x (x < 0.5, KLN) crystals are very promising for blue-light second harmonic generation, and their growth conditions are important to know. For this purpose, the limit of the solid solution range in the 30 mol% K 2O isopleth of the ternary system Li 2O–K 2O–Nb 2O 5, to which KLN crystals belong, was investigated by powder X-ray diffraction (XRD). Several crystals with different compositions x were also pulled by the LHPG (laser-heated pedestal growth) technique and characterized by energy-dispersive system (EDS) microprobe analysis, absorption spectra measurements, phase matching studies, and Raman microspectroscopy.

Determination of trace cerium in doped crystal Ce∶K3.0Li2.0Nb5.0O15.0by ICP-MS

In this paper, an accurate and simple method is described for the determination of trace cerium in doped potassium lithium niobate (Ce∶KLN) crystals by inductively coupled plasma mass spectrometry (ICP-MS). The KNbO3 multiplying frequency of an AsAlGa diode may be replaced with a K3.0Li2.0Nb5.0O15.0 (KLN) crystal laser in order to obtain blue light. The storage time of blue light is 4 times better than that of red light. Therefore, KLN crystals offer excellent application. However, the photorefractive properties of Ce∶K3.0Li2.0Nb5.0O15.0 (Ce∶KLN) crystals depend upon the doping concentration of cerium. Samples were digested with concentrated sulfuric acid and hydrogen peroxide. The determination of cerium was carried out using external calibration with matrix matched standards and high-purity spiking material. The detection limit of Ce was 7 pg ml–1. The recovery was 85 to 107%. The relative standard deviation was 3.0 to 3.8%. The doping concentration of cerium in KLN crystals was 97.6 µg g–1.

Growth and characterization of K 3Li 2− xNb 5+ xO 15+2 x single crystals obtained by the edge-defined film-fed growth technique

K 3Li 2− x Nb 5+ x O 15+2 x (KLN) crystals with large size (20×15×30 mm 3), high Li-contents (1.8–1.97) and free of cracks were successfully grown by the “edge-defined, film-fed growth” technique. The advantages of the technique used for the growth of KLN crystals were demonstrated and optimal growth conditions were found. The crystals obtained by this method have high-quality and good second-harmonic generation property.

RECENT DEVELOPMENTS IN THE GROWTH AND CHARACTERIZATION OF POTASSIUM LITHIUM NIOBATE (KLN) CRYSTALS FOR DIRECT DOUBLING OF SEMICONDUCTOR LASERS

This paper reports the successful growth of crystals of the potassium lithium niobate (KLN) family having a non-centred tungsten bronze structure. Crack free crystals up to 20 mm in diameter by 30 mm in length have been grown reproducibly by the top-seeded solution growth (TSSG) method from K+ and Li+ rich solutions. These crystals form solid solutions in which both the structural and optical properties vary with composition. Birefringence measurements show that KLN crystals may be non-critically phase matched for second harmonic generation in the wavelength range 1050 nm to 820 nm at room temperature, depending on composition. The ability to tune the optical properties in this way makes KLN an ideal candidate for direct doubling of semiconductor lasers. © 1998 Chapman & Hall

Growth and Characterization of K3Li2-xNb5+xO15+2x Micro Single Crystals Formed by the µ-Pulling Down Method for Blue SHG Applications

Potassium lithium niobate ( K3Li2-X Nb5+X O15+2X : KLN) crystals are difficult to grow by conventional crystal growth methods because of the distinct change of composition. Using the micro pulling down ( µ-PD) method, crack-free and homogeneous KLN crystals with a length of 150 mm and diameters of 150, 300 and 500 µm have been grown successfully. The crystals show good structural quality, single-domain structure and an excellent second harmonic generation property. The red irradiation of a Ti: sapphire laser and semiconductor laser diode was converted by µ-PD crystals to blue laser light with half wavelength.

Growth and properties of tungsten bronze K 3Li 2Nb 5O 15 single crystals

Tetragonal tungsten bronze K 3Li 2Nb 5O 15 (KLN) single crystals have been grown up to 8 – 10 mm diameter and 40 – 50 mm long using the Czochralski technique. Crystal growth was studied in various orientations with growth along 〈100〉 and 〈110〉 being relatively easier than along 〈001〉. Crystals grown along 〈001〉 have a square cross-section similar to other bigger unit cell bronzes such as Ba 2−xSr xK 1−yNa yNb 5O 15 (BSKNN). Like BSKNN, KLN crystals show strong longitudinal effects, such as ε 11, k 15, d 15 and r 51, indicating suitability for Surface Acoutic Wave (SAW), electro-optic and photorefractive applications.