Borate Crystals Research Articles

χ (2)-induced artifact overwhelming the third-order signal in 2D Raman-THz spectroscopy of non-centrosymmetric materials.

Through comprehensive data analysis, we demonstrate that a χ(2)-induced artifact, arising from imperfect balancing in the conventional electro-optic sampling detection scheme, contributes significantly to the measured signal in 2D Raman-THz spectroscopy of non-centrosymmetric materials. The artifact is a product of two 1D responses, overwhelming the desired 2D response. We confirm that by analyzing the 2D Raman-THz response of an x-cut beta barium borate crystal. We furthermore show that this artifact can be effectively suppressed by implementing a special detection scheme. We successfully isolate the desired third-order 2D Raman-THz response, revealing a distinct cross-peak feature, whose frequency position suggests the coupling between two crystal phonons.

First Achievement of Yellow Laser Operation in Dy3+-Doped Borate Crystals.

Continuous-wave (CW) yellow lasers have been demonstrated successfully by using a GaN laser-diode (LD) pumping in borate crystals for the first time. The Dy3+:GdMgB5O10 (Dy:GMB) crystal with dimensions up to 33 × 19 × 15 mm3 is grown by the top-seeded solution growth method, and the polarized spectroscopic properties are investigated systematically at room temperature. The line strengths, Judd-Ofelt (J-O) intensity, spontaneous transition rates, fluorescence branching ratios, and radiative lifetimes are calculated in detail by the Judd-Ofelt theory. Under direct pumping of 452 nm LD, a compact continuous-wave yellow laser with a maximum output power of 628 mW and laser wavelength of 581 nm is generated based on a Y-cut Dy:GMB crystal. To our knowledge, it is not only the highest output power for yellow laser obtained in Dy3+-doped crystals but also the first yellow laser operation achieved by borate crystals under direct LD pumping. The results reveal that the Dy:GMB crystal is an optical material with important application prospects in yellow laser.

Breaking through the ‘‘200 nm deep-ultraviolet wall’’ of phase matching region by cation structural modulation

Adjusting birefringence to push the phase-matching (PM) of nonlinear optical (NLO) crystals blue-shifting to the deep-ultraviolet (DUV) region is the inorganic chemists and material scientists' pursuit, while refractive dispersion as an important but easily overlooked optical properties generally brings the unexpected result. Herein, two new Y-based borates, K2YB3O6F2 and Rb2YB3O6F2 have been synthesized by the modulation of A-site cation. In both structures, owing to the structure-directing properties of Y-based polyhedra, the natural advantage of π-conjugated [B3O6] groups was pushed to the greatest extent, theoretical calculations and structure analysis revealed that the coplanar arrangement of [B3O6] groups results in the large birefringence of K2YB3O6F2 and Rb2YB3O6F2. Importantly, the aligned orientation of [B3O6] rings makes Rb2YB3O6F2 possess a strong SHG response of 5.0 × KDP, meanwhile the small dispersion of the refractive indices makes Rb2YB3O6F2 the first borate crystal containing the strong π-conjugation [B3O6] rings with the PM limit breaking through the ‘‘200 nm DUV wall’’. This work indicates that refractive dispersion can be effectively reduced through the cation effect, thereby broadening the PM range.

A Rare-Earth-Based Borate Optical Crystal with Enlarged Dihedral Angles of Distinct [BO3] Groups Exhibiting a Wide UV Transparent Range.

Borates, as advanced optical materials, have garnered wide interest due to their diverse structural configurations and great potential for applications in the ultraviolet (UV) regions. Herein, we synthesized a new rare-earth borate crystal, namely, K2NaYB2O6, which is classified as one of the ABReB2O6 compounds, where A and B represent alkali metal and Re denotes rare-earth metal. K2NaYB2O6 adopts in the monoclinic space group P21/c (No. 14), showcasing a three-dimensional (3D) framework composed of a planar triangular configuration of [BO3] units and distortive [YO7] polyhedra. Notably, both dihedral angles between distinct [BO3] units reach 79.6°, which represents an unprecedented structural feature in monoclinic ABReB2O6-type crystals. Moreover, the compound has a short UV absorption edge at around 204 nm, corresponding to a wide band gap of approximately 5.67 eV. Additionally, it possesses a moderate birefringence of 0.028 at 1064 nm. Further analysis utilizing theoretical calculations suggests that the optical behaviors of K2NaYB2O6 are mainly governed by its basic structural unit [BO3] triangles and distorted [YO7] polyhedra. These findings enrich the structure chemistry of rare-earth borates and offer valuable insights for the design of optical crystals in the UV wavelength range.

Jahn-Teller effect and features of divalent copper ion behavior in multicomponent borate crystals

Crystals of YGa3(BO3)4, YAl3(BO3)4, EuGa3(BO3)4 and EuAl3(BO3)4 with copper alloy were studied by electron paramagnetic resonance and X-ray diffraction analysis. The lattice parameters and coordinates of copper-doped boron atoms were determined. The study of EPR spectra showed that copper is in the divalent state and replaces aluminum ions with C2 node symmetry. In YAl3(BO3)4:Cu crystals, a ligand structure exists due to the interaction of copper electrons with yttrium nuclei. The parameters of the spin Hamiltonian describing the behavior of the Cu2+ spectrum have been determined. The deviation of the Z-axis spectra from the C3 axis by 54(1)° is due to Jahn-Teller vibronic interaction and monoclinic distortion. In the EuGa3(BO3)4 crystal, a new spectrum 2 was found, which also belongs to divalent copper but is observed at an excited state 31 cm−1 away from the ground state. Above 70 K, an isotropic EPR line with a width of 450 Gs, g = 2.1, appears and exists up to room temperature.

Integrated optical waveguides for quantum photon gates at a wavelength of 810 nm

Subject of study. The optical losses in waveguides designed for creating quantum photon gates at a wavelength of 810 nm were investigated. Aim of study. The aim of the study was to create integrated optical single-mode waveguides for quantum photon gates at a wavelength of 810 nm and to estimate optical losses acceptable for maintaining the necessary degree of photon-pair entanglement. Method. The waveguides were manufactured through thermal diffusion of titanium ions into a substrate composed of an X-slice of nominally pure lithium niobate (LiNbO3). Optical losses were estimated by experimentally measuring the loss per unit length of the waveguide. Optical radiation was coupled into and out of the waveguide using fiber segments, with one end connected and the other cleaved. A drop of immersion liquid was applied between the cleaved fiber and waveguide end, and measurements were performed for both polarization modes. Main results. Six groups of samples were produced, each containing waveguides with strip widths of d=3.0, 2.0, and 1.5 µm. The measured optical losses in the manufactured waveguides indicated that those with a titanium strip width of d≈3 µm exhibited the lowest losses. The estimated minimum optical losses for transverse magnetic and transverse electric polarization were approximately 0.20–0.25 and 0.1 dB/cm, respectively. Practical significance. The waveguides manufactured with a strip width of approximately 3 µm can be used to create quantum photonic gates in an integrated optical design. The chosen wavelength of 810 nm offers potential for near-future development of photonic gates, as one of the most accessible methods for generating entangled photon pairs involves using a 405-nm laser followed by wavelength doubling through a nonlinear beta-barium borate crystal.

KNa2Lu(BO3)2: A Rare-Earth Borate Crystal Characterized by an Enhanced Birefringence and Wide Ultraviolet Transparency Range.

Borate materials are of significant interest due to their versatile structural configuration and competitive ultraviolet (UV) transparency range. In this study, we present a novel rare-earth borate crystal, KNa2Lu(BO3)2, synthesized for the first time through a facile spontaneous crystallization method. It adopts the centrosymmetric space group Pnma (no. 62) and yields a unique three-dimensional (3D) structural network formed by isolated [BO3] plane triangles and distorted [LuO7] polyhedra. This compound displays excellent thermal stability up to ∼990 °C, demonstrating a favorable congruent melting nature. Moreover, KNa2Lu(BO3)2 achieves a notably short UV absorption cutoff at approximately 204 nm, yielding a large band gap of 5.58 eV. Remarkably, it showcases an enlarged birefringence of 0.044 at 1064 nm, implying its potential as a birefringent material. Moreover, density functional theory calculations demonstrate that the optical characteristics are predominantly influenced by fundamental building blocks [BO3] triangles and distorted [LuO7] polyhedra. Our findings demonstrate the potential of KNa2Lu(BO3)2 in the development of a birefringent candidate and enrich the structural chemistry of rare-earth-based borates.

Deciphering the structure and potassium-ion transport mechanism of potassium borate glass.

Potassium borate glass has great potential as an ion transport material. The ion transport rate is closely related to the microstructure of the glass. However, the disorder and variations in boron and oxygen atom types in the glass structure pose challenges in the analysis of this complex glass structure. In this work, the structure of potassium borate glass was unveiled through the neutron diffraction method and ab initio molecular dynamics (AIMD) simulations. The B-O, K-O, and O-O atomic interactions, bond lengths, coordination numbers, cavity distribution, ring structure distributions and other detailed information in the microstructure of potassium borate glass were obtained. By comparing the structure and properties of potassium borate glass with those of crystals of similar components, it is found that the bond lengths of 3B-BO (BO, bridging oxygen), 4B-BO and 3B-NBO (NBO, non-bridging oxygen) are longer than those of corresponding crystals, so the structure of the boron-oxygen network is looser and the density is smaller than that of similar crystals. Moreover, we found a rule that in both borate glass and crystal, the increase of NBO shortened the length of the B-O bond, and the increase of 4B increased the length of the B-O bond. The key structures affecting the transport rate of K+ were NBO, chain structure units and cavities. This work will provide reference data for designing and developing electrically conductive amorphous materials with faster potassium-ion transport rates.

Multiple visible wavelength switchable cascaded self-Raman laser based on selective wave-mixing mechanism

A diode-pumped solid-state laser with watts-level five switchable wavelengths spanning green to red is first experimentally demonstrated. The selective wave-mixing mechanism was introduced for multiple visible wavelength switchable output. The five visible wavelengths are generated by wave-mixing of the fundamental wave, the first-Stokes wave, and the second-Stokes wave in a Nd:YVO4 self-Raman laser. A β-barium borate crystal with a critical phase-matching angle cut is used for the wavelength conversion, and the angle-tuning method was used to achieve fast wavelength switching. A diffusion bonded YVO4/Nd:YVO4/YVO4 crystal was used to reduce the thermal lens effect and increase the effective length of the Raman gain medium for high output power and efficient Raman conversion. Under a pump power of 19.5 W, five visible laser output powers achieved for the green at 532 nm, lime at 559 nm, yellow at 588 nm, orange-red at 620 nm, and deep red at 657 nm are 4.01, 1.76, 2.54, 1.41, and 2.82 W, respectively. This laser system provides a convenient way for visible wavelength-switchable coherent light generation and may find potential applications where multiple visible wavelengths are required.

Generation of millijoule-level sub-5 fs violet laser pulses

AbstractWe demonstrate the generation, spectral broadening and post-compression of second harmonic pulses using a thin beta barium borate (BBO) crystal on a fused-silica substrate as the nonlinear interaction medium. By combining second harmonic generation in the BBO crystal with self-phase modulation in the fused-silica substrate, we efficiently generate millijoule-level broadband violet pulses from a single optical component. The second harmonic spectrum covers a range from long wave ultraviolet (down to 310 nm) to visible (up to 550 nm) with a bandwidth of 65 nm. Subsequently, we compress the second harmonic beam to a duration of 4.8 fs with a pulse energy of 0.64 mJ (5 fs with a pulse energy of 1.05 mJ) using chirped mirrors. The all-solid free-space apparatus is compact, robust and pulse energy scalable, making it highly advantageous for generating intense second harmonic pulses from near-infrared femtosecond lasers in the sub-5 fs regime.

Luminescence and Excited State Dynamics of Tb1-XEuxAl3(BO3)4 (x=0.01-0.20)

The room temperature luminescence spectra and emission decay curves of undoped and Eu3+-doped TbAl3(BO3)4 crystals, grown using the flux growth technique, are presented and discussed. The experimental results show that excitation of the Tb3+ excited states gives rise to 5D0 emission from the Eu3+ ion, and therefore non-radiative energy transfer involving the two ions is operative. Analysis of the experimental data indicates that the excitation of the Tb3+ donor ion gives rise to fast energy migration in the 5D4 level of the Tb3+ subset of cations, followed by the energy transfer process populating the 5D0 level of Eu3+. Upon increasing the Eu3+ acceptor concentration, the mainly green emission intensity and the decay time of the 5D4 level decrease, whilst the red emission of 5D0 becomes dominant. The experimental data are interpreted on the basis of the trigonal huntite-type structure of the double borate crystals under investigation.

Fluorination Strategy Towards Symmetry Breaking of Boron‐centered Tetrahedron for Poly‐fluorinated Optical Crystals

AbstractBorate crystals can be chemically and functionally modified by the fluorination strategy, which encourages the identification of emerging fluorooxoborates with a structure and set of characteristics not seen in any other oxide parents. However, the bulk of fluorooxoborates have been found accidentally, rational methods of synthesis are required, particularly for the infrequently occurring poly‐fluorinated components. Herein, we reported the use of bifluoride salts as a potent source of fluorine to prepare fluorooxoborates that contain rarely tri‐fluorinated [BF3X] (X=O and CH3) tetrahedra and eleven compounds were found. We identified the optical properties of the organofluorinated group [CH3BF3] and their potential for nonlinear optics for the first time. Among these, two non‐centrosymmetric components hold potential for the production of 266 nm harmonic coherent light for nonlinear optics, and more crucially, have the benefit of growing large size single crystals. Our study establishes experimental conditions for the coexistence of the diverse functional groups, enabling the production of poly‐fluorinated optical crystals.

Fluorination Strategy Towards Symmetry Breaking of Boron-centered Tetrahedron for Poly-fluorinated Optical Crystals.

Borate crystals can be chemically and functionally modified by the fluorination strategy, which encourages the identification of emerging fluorooxoborates with a structure and set of characteristics not seen in any other oxide parents. However, the bulk of fluorooxoborates have been found accidentally, rational methods of synthesis are required, particularly for the infrequently occurring poly-fluorinated components. Herein, we reported the use of bifluoride salts as a potent source of fluorine to prepare fluorooxoborates that contain rarely tri-fluorinated [BF3 X] (X=O and CH3 ) tetrahedra and eleven compounds were found. We identified the optical properties of the organofluorinated group [CH3 BF3 ] and their potential for nonlinear optics for the first time. Among these, two non-centrosymmetric components hold potential for the production of 266 nm harmonic coherent light for nonlinear optics, and more crucially, have the benefit of growing large size single crystals. Our study establishes experimental conditions for the coexistence of the diverse functional groups, enabling the production of poly-fluorinated optical crystals.

Magnetic structure of mixed iron-gallium borate crystals: EMR and SQUID studies

Iron-gallium borate, FexGa1−xBO3, single crystals have been synthesized by the solution in the melt technique. The exact x-values in the crystals have been determined by X-ray fluorescence analysis and checked by Energy Dispersive X-Ray Spectroscopy. Scanning Electron Microscopy has been used to map distributions of iron and gallium ions in the crystals. The electron magnetic resonance (EMR) spectra as well as field and temperature dependences of the magnetization obtained by SQUID reveal the existence of different magnetic phases in different x ranges, viz. weakly ferromagnetic antiferromagnetic, magnetic cluster and paramagnetic phase. For crystals with 0.32 ≤ x ≤ 0.83, the Néel temperatures, TN, have been determined. The magnetometry of these crystals suggests the existence of another magnetic transition at a temperature well below TN, tentatively ascribed to a Morin type transition. Detailed EMR and SQUID studies of the crystal with x ≈ 0.2 reveal the existence of magnetic nanoclusters showing superparamagnetic behaviour. Using a laboratory developed code based on the Monte-Carlo technique, spatial distributions of dia- and paramagnetic ions in the crystal with x ≈ 0.2 has been visualized and possible cluster sizes have been estimated.

Symmetry invariants of higher orders in magnetoelastic energy for a trigonal easy-plane antiferromagnet

In expansion of the thermodynamic potential for a trigonal easy-plane antiferromagnet such as iron borate, FeBO3, magnetoelastic invariants of a higher order in the components of the deformation tensor and the antiferromagnetic vector with respect to those traditionally used were taken into account. Such invariants make it possible to describe new effects observed in iron borate crystals and composites based on them.

Electro-optic effects of lithium borate crystals studied by first-principles method

In respect to the electro-optic (EO) effect, LiB3O5 (LBO) and Li2B4O7 (LB4) contain the same elements but represent two extremes in the family of nonlinear optical (NLO) borate crystals: one with large second harmonic generation (SHG) coefficients but very small reported EO coefficients, the latter has extremely small SHG coefficients yet EO coefficients were found even larger than the practical EO modulator crystal β-BaB2O4 (BBO). The puzzle was unraveled through first-principles studies of the two crystals and it is found that the vibrational and electronic contributions to the EO effect were canceled in LBO and the major contributions are from piezoelectric induced effect for LB4 with electronic contributions negligible. In addition to the EO and NLO coefficients, dielectric, elastic, piezoelectric and elasto-optic constants are all obtained simultaneously. More importantly, fully determining the elastic, elasto-optic constants, all 4th rank tensors, can be adopted to calibrate the experimental uncertainties and help to design practical surface acoustic wave (SAW) or acoustic optic modulator (AOM) devices.

An investigative study on optical and dielectric characteristics of Thiourea Cadmium Hydrogen Borate NLO crystal for photonic applications

Single crystals of Thiourea Cadmium hydrogen borate (TCHB), a hybrid nonlinear optical (NLO) material, are grown from an aqueous solution by slow evaporation solution growth technique at ambient temperature. Characterization studies have been conducted to probe the nonlinear effects of the crystal. The crystalline nature of TCHB is explored using the single crystal X-ray diffraction technique. The chemical composition is resolved by the Fourier transform infrared (FTIR) spectroscopy and energy dispersive X-ray analysis. UV–Vis spectral studies analyze the transparency of the crystal. Optical studies illustrate the UV cut-off wavelength to be 285[Formula: see text]nm with wide window of transparency in the infrared and visible regions. The optical and electrical conductivity studies indicate superior optical response essential for optical computing and photonic applications. The Kurtz powder test has confirmed the NLO capability. The thermal stability is analyzed through a thermogravimetric study. Dielectric and AC conductivity measurements carried out over a wide range of frequencies (100[Formula: see text]Hz to 5[Formula: see text]MHz) for various temperatures establish the semiconducting and photonic capacity of TCBH crystal to be used as photodiodes, optical fibres and laser lights.

Generation of high-energy near-infrared femtosecond laser pulses by optical parametric amplification in YCOB crystals

"The energy of near-infrared femtosecond laser pulses generated by optical parametric amplification (OPA) in β-barium borate (BBO) crystals pumped by femtosecond Ti:sapphire lasers is restricted to few-mJ due to the 20 mm limited diam- eter of available crystals. In a type I collinear OPA with an yttrium calcium oxoborate (YCOB) crystal, pumped with femtosecond Ti:sapphire lasers at 800 nm wavelength, the 1300 nm signal wavelength and 2080 nm idler wavelength are located in the normal and anomalous group velocity dispersion range, respectively. Due to the small group velocity mismatch (GVM) between signal and idler pulses, as broad as 27 THz gain bandwidth can be obtained in a 3-mm YCOB crystal at 100 GW/cm2 pump intensity. A high parametric gain is the result of the increased parametric interaction length due to the different signs of GVM between pump-signal and pump-idler pulses. More than 10-mJ energy femtosecond laser pulses at 1300 nm wavelength can be generated by OPA in YCOB crystals with larger than 50 mm clear aperture."

Synthesis and Crystal Structure of a Novel Organo-Inorganic Hybrid Borate, K[B5O6(OH)4][B(OH)3]2(H2O)(C10H20O5)2

Crystals of a novel hybrid organo-inorganic borate, K[B5O6(OH)4][B(OH)3]2(H2O)(C10H20O5)2 (1), were obtained from aqueous solutions and characterized by single-crystal X-ray diffraction and IR spectroscopy. 1 is triclinic (a = 10.1567(4), b = 11.9941(6), c = 17.1893(9) Å, α = 75.280(4), β = 79.406(4), γ = 88.531(4)°, V = 1990.270369 Å3, SG P-1; R1 = 0.058). Its structure contains [K(C10H20O5)2]+ groups which behave as “hydrophobic” templates for the inorganic part comprised of B5O6(OH)4 anions and neutral B(OH)3 molecules.

Complex of Laboratory Growth Facilities for Solution–Melt Synthesis Crystals of Iron Borate FeBO3 and Crystals of Solid Solutions on Its Basis

Complex of Laboratory Growth Facilities for Solution–Melt Synthesis Crystals of Iron Borate FeBO3 and Crystals of Solid Solutions on Its Basis