Promising Nonlinear Optical Crystal Research Articles

Orange, yellow and green emissions generated in Q-switched Nd:YALO3/YVO4 Raman laser

Nd:YAlO3/YVO4 crystal Raman laser with orange, yellow and green emission switchable output was demonstrated by the second-harmonic generation and sum-frequency generation of the fundamental and the first-Stokes waves. A diode-end-pumped acousto-optic Q-switched Nd:YAlO3 crystal laser at 1080 nm was used to drive a 30 mm length YVO4 crystal for intra-cavity Raman operation. The different visible sources were achieved in an angle-tuned BBO crystal. The average output power of 539.9 nm green light, 567.2 nm yellow light and 597.4 nm orange light generated in a BBO crystal with single direction were 418, 266 and 361 mW at an absorbed pump power of 6.01 W and a pulse repetition frequency of 20 kHz, with respective to pulse widths of about 47.2, 4.8 and 5.6 ns. The results show that the angle-tuned BBO crystal with characteristics of large temperature tolerance and large nonlinear optical coefficient was a promising nonlinear optical crystal for wavelength-switching in the Q-switched Raman laser.

1.21-W 532-nm picosecond green laser generated by second-harmonic generation using K3B6O10Cl as a nonlinear optical crystal

We demonstrated a 1.21-W 532-nm picoseconds (ps) green laser via second-harmonic generation (SHG) using type-I phase-matched K3B6O10Cl (KBOC) as a nonlinear optical crystal. The ps green laser was successfully generated from two types of 1064-nm ps lasers with one being operated at 10 kHz and the other at 10 Hz. Using a 7.38-W pumping power at 10 kHz as the pump, the SHG output power at 532 nm was 1.21 W with a pulse width of 34.4 ps. For the 10-Hz ps laser with pumping energy of 4.95 mJ per pulse, the output at 532 nm was 1.78 mJ per pulse, which corresponds to an optical conversion efficiency of 36.0%. The experimental results show that the KBOC crystal is a promising nonlinear optical crystal for generating ps green laser.

Electronic, optical, infrared, and elastic properties of KCdCO3F from first principles

KCdCO3F is a newly synthesized promising ultraviolet nonlinear optical crystal, but its structure is disputed and its fundamental properties have not been well studied. Here our first-principles study indicates that the structure with the space group P6¯c2 is energetically more stable than the P6¯m2 phase. We systematically investigated its electronic, optical, vibrational, infrared, and elastic properties. The results reveal that KCdCO3F is a direct-band-gap insulator with rather flat bands below the Fermi level. Analyses of its partial density of states revealed that the top (bottom) of its valence (conduction) band is formed by the O 2p (Cd 5s) orbital. It is a negative uniaxial crystal with ionic-covalent nature. Both infrared-active and Raman-active modes exist at its Brillouin zone center, and ions contribute more to its static dielectric constants. Its optical spectra in the visual and infrared ranges were studied, and their origins were revealed. Calculations indicate that KCdCO3F is mechanically stable but anisotropic since it is more vulnerable to shear stress and is easy to cleave along the c axis.

Investigations on the Nucleation Kinetics, Growth and characterization of Glycine Rubidium Chloride (GRC): a promising nonlinear optical single crystal

Investigations on the Nucleation Kinetics, Growth and characterization of Glycine Rubidium Chloride (GRC): a promising nonlinear optical single crystal

Study of the vibrational, dielectric and infrared properties of CdSiP 2 via first principles

CdSiP2is a promising nonlinear optical crystal for frequency conversion in the mid-IR spectral range. In this work, the vibrational, dielectric and infrared properties of CdSiP2 are studied by using density functional perturbation calculation. The Born effective charges of the constituent ions, the vibrational modes and the splitting of the longitudinal and transverse optical (LO–TO) frequencies at the Brillouin zone center are calculated and discussed. Its dielectric constant and dielectric spectra are also calculated, which reveals that electrons in CdSiP2 have a larger contribution to the dielectric constant than the lattice. The theoretically obtained birefringence Δn and the simulated infrared reflectance spectra agree well with the available experimental results.

Strain engineering of nonlinear boron phosphate for phase matching in the ultraviolet region: a first-principles study

Borophosphates, particularly BPO4 (BPO) crystals, have attracted attention in laser frequency conversion devices because of their short ultraviolet cutoff edge and relatively large second harmonic generation (SHG) response, which is almost twice as great as that of KH2PO4. However, the birefringence of BPO (approximately 0.005) is too small to satisfy the phase matching condition in the ultraviolet spectral region, restricting the laser output efficiency. Here we systematically examine the influence of mechanical strains on the atomic structure as well as the electronic and optical properties of BPO using first-principles calculations. Interestingly, we find that the birefringence of BPO can be enhanced by ~0.06 through external uniaxial strain along the c-axis. Meanwhile, compressive strain can increase the band gap and SHG coefficients effectively. Refractive-index dispersion is also emphasized in this work. Our results indicate that phase matching in the ultraviolet region (266 nm) can be achieved under −10% strain (3.9 GPa). This investigation is helpful for understanding the structure–property relationship of BPO under strain, and it also indicates its possible use as a promising ultraviolet nonlinear optical crystal.

Thermo-physical properties of nonlinear optical crystal K3B6O10Br

The thermo-physical properties of the nonlinear optical (NLO) crystal K3B6O10Br (KBB) were experimentally investigated, including specific heat, thermal conductivity, coefficient of thermal expansion and refractive index. The specific heat of KBB is lower than that of LiB3O5 and higher than that of other borate NLO crystals, such as β-BaB2O4, CsLiB6O10 and CsB3O5, and KBB manifests a high damage threshold because of its lower temperature gradient during laser pulse irradiation. The thermal expansion coefficients were obtained as α x = 5.09 × 10−6 K−1 and α z = 2.39 × 10−5 K−1, showing weaker anisotropy than those of commonly used NLO crystals. The temperature-dependent Sellmeier dispersion equations of the refractive indices were also obtained, and the phase-matching angles for second harmonic generation (SHG) at temperatures of 313, 343, 373, 403 and 433 K which were calculated from these equations are in good agreement with the experimental values. All results are indicative of the KBB crystal as a novel promising NLO crystal for high power SHG.

Growth, non-linear optical, photoconductivity and dielectric characterization of pure and EDTA doped tris-glycine zinc chloride single crystals for LiDAR

Non-linear optical crystals which are used as frequency converters to access various spectral ranges like visible or UV are key components of (Light Detection and ranging) LiDAR systems. For this purpose promising non-linear optical crystals like tris-glycine zinc chloride (TGZC) a nonlinear optical material, with the additive Ethylenediaminetetraacetic acid (EDTA) is grown successfully by slow cooling technique. In order to improve the device characteristics of TGZC crystals, organic dopant EDTA were incorporated into the parent crystals. Observation of the crystal growth, behavior and measurement of growth kinetics revealed a strong dependence of growth rate on the additive. The slight change in unit-cell parameters of the doped compound from the pure TGZC were confirmed by single crystal X-ray diffraction analysis. The presence of functional groups is estimated qualitatively by FTIR analysis. The UV–vis spectrum shows a cut-off wavelength less than 300nm. The photocurrent of both pure and doped crystals is more than that of the dark current. Microhardness studies carried out using Leitz Weitzler hardness tester at room temperature showed an increase due to doping. The dielectric loss is low at high frequency and this behavior is of vital importance for NLO applications. In this paper, an attempt has been made on the growth and characterization of nonlinear optical crystal and theoretical aspects of single crystals as frequency convertors in Atmospheric Remote Sensing is discussed.

Synthesis, growth and characterization of a new promising organic nonlinear optical crystal: 4-Nitrophenyl hydrazone

4-Nitrophenyl hydrazone single crystals were grown by slow evaporation of solvent method using acetone as a solvent. The grown crystals were subjected to various characterizations such as X-ray diffraction studies, UV–visible studies, thermogravimetric analysis and differential thermal analysis (TGA/DTA) and second harmonic generation (SHG). The cell parameters were calculated by using single crystal XRD measurement and the crystal system was found as orthorhombic with non-centro-symmetric space group Pca21. The crystallinity of the grown crystal was confirmed by powder X-ray diffraction analysis. The Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) studies confirmed the presence of functional groups in the sample. The optical transmittance spectrum shows that the crystal is transparent in the visible wavelength range. The scanning electron microscopy (SEM) was used to study the surface morphology of the grown crystal. The chemical composition of the grown crystal was confirmed by energy dispersive X-ray (EDX) analysis. The TGA/DTA results showed that the material is stable up to 146°C. The NLO property of the crystal was confirmed by Kurtz and Perry method and SHG conversion efficiency is 15.39 times when compared to KDP crystal.

Beryllium-free Rb3Al3B3O10F with reinforced interlayer bonding as a deep-ultraviolet nonlinear optical crystal.

A new beryllium-free borate Rb3Al3B3O10F has been synthesized and characterized by single-crystal X-ray diffraction. It features a framework structure consisting of alveolate [Al3(BO3)3OF]∞ layers tightly bound via Al-O and Al-F bridged bonds, with the in-layer [BO3](3-) groups in nearly coplanar and aligned arrangement. This compound is transparent down to 200 nm and is phase-matchable with a powder second-harmonic generation efficiency of 1.2 times that of KH2PO4. Remarkably, it exhibits a strong interlayer bonding which is about one order larger than that of the benchmark KBe2BO3F2, thus no layering tendency was observed during the crystal growth. In addition, it is nonhygroscopic and thermally stable up to ∼1462 K. These attributes make Rb3Al3B3O10F a promising nonlinear optical crystal in the deep-ultraviolet region. First-principles calculations, combined with the anionic group theory, were adopted to rationalize the optical properties.

Synthesis, structure, crystal growth and characterization of a novel semiorganic nonlinear optical l-proline lithium bromide monohydrate single crystal

l-Proline lithium bromide monohydrate (LPLBM), a promising semiorganic nonlinear optical material, was synthesized and single crystals of LPLBM were grown from solution by slow evaporation technique. Single crystal X-ray structure solution reveals that the grown crystal belongs to monoclinic system with space group P21. Presence of various functional groups was identified by FT-IR and FT-Raman spectral analyses. UV–Vis–NIR spectroscopic study shows that the LPLBM crystal possesses 90% of transmittance in the range of 250–1100nm. Vickers microhardness values, the dielectric constant and dielectric loss of the LPLBM crystal were reported. Elemental analysis by energy dispersive X-ray analysis shows the presence of carbon, nitrogen, oxygen and bromine. The surface morphology of the crystal was investigated using scanning electron microscopic study. The thermal stability of the LPLBM crystal was studied from TGA and DSC analysis. Second harmonic generation efficiency of the LPLBM crystal measured by Kurtz and Perry powder technique using Nd:YAG laser is about 0.3 times that of urea.

Novel Study on Determination of Crystal Growth Conditions for L-arginine Phosphate Monohydrate Crystal by Ultrasonic Velocity Measurement in Aqueous Solution of L-arginine and Phosphoric Acid

Low temperature solution growth technique is a versatile and low cost technique to grow single crystals of good quality. Before crystal growth, it needs to decide solvent and growth temperature by studying solubility at different temperatures in different solvents, and pH of the growth solution. Metastable zone width and induction period are other important parameters considered during crystal growth. We have presented a simple, cost effective test to decide growth temperature, solution pH and proportion of different components (in case of multi-component compounds) of compound in the solution to grow quality single crystals with optimum growth rate. L-arginine phosphate monohydrate is a promising nonlinear optical crystal and we have successfully attempted to study the optimum pH and proportion of L-arginine and phosphoric acid in the solution for crystal growth by measuring ultrasonic velocity and determining related thermodynamic parameters.

A promising new nonlinear optical crystal with high laser damage threshold for application in the IR region: synthesis, crystal structure and properties of noncentrosymmetric CsHgBr3

A new phase of CsHgBr3with a noncentrosymmetric crystalline structure is synthesised and shows high laser damage threshold and nonlinear optical properties.

Pb3B6O11F2: the first non-centrosymmetric lead borate fluoride with a large second harmonic generation response

The introduction of Pb2+ cations with the lone pair effect and the largest electronegativity of F− anions successfully results in a new non-centrosymmetric lead borate fluoride, Pb3B6O11F2, which possesses a large SHG response about four times that of KH2PO4 (KDP) and is type-I phase matchable. The structure is built from a 3-dimensional B–O network composed of hexaborate B6O14 groups and novel [FPb3]∞ layers. First-principles electronic structure calculations show that the calculated birefringence of Pb3B6O11F2 is about 0.07 in the visible region. Based on the measurement of the UV–Vis–NIR diffuse-reflectance spectrum, it exhibits a wide transparency range with a short UV cut-off edge at about 240 nm. All these properties indicate that Pb3B6O11F2 is a promising nonlinear optical crystal in the UV region.

Growth, structure and optical properties of an efficient NLO crystal-aqua maleatocopper(II)

A promising non-linear optical (NLO) crystal, aqua maleatocopper(II) (CuC4H2O4·H2O), was grown at room temperature by the controlled ionic diffusion technique. Fourier transform infrared spectrum could identify the various functional groups in the crystal. Structural analysis using single crystal XRD revealed that the compound crystallizes in the monoclinic system with space group P21 and unit cell parameters a=7.7277(5)Å, b=5.2967(3)Å, c=7.7179(4)Å, α=γ=109.170(5)°, β=111.995(2)°. The thermal stability and decomposition pattern of the material were explored using thermogravimetry (TG) and differential thermal analysis (DTA). The optical band gap energy of the material was estimated as 2.2eV from the diffuse reflectance spectroscopy. The Kurtz and Perry powder technique established the crystal to be an efficient non-linear optical (NLO) material.

Liquid phase growth of bulk GaSe crystal implemented with the temperature difference method under controlled vapor pressure

GaSe crystal has been expected as one of the promising nonlinear optical crystals for highly efficient terahertz (THz) wave generation. However there are several reasons why it is difficult to grow the bulk crystals with high quality. To overcome some difficulties, the temperature difference method under controlled vapor pressure (TDM-CVP) is applied for crystal growth. According to this method, stoichiometric composition can be controlled by the application of Se vapor during crystal growth. Crystal growth is carried out at a constant growth temperature without any mechanical disturbance or vibration. It is also noticed that lower temperature growth enables the reduction of point defect concentration in equilibrium. In this article, surface morphology is observed by an optical microscope using the Nomarski interference method. To identify polytypes of grown crystals, backscattered Raman spectra were measured. X-ray diffraction confirmed the polytypes and single crystalline phase. Infrared (λ=1μm) and terahertz wave (1–3THz) transmittance measurements were performed to calculate the absorption coefficient in these wavelength regions. From these results, it is shown that the grown crystals have shown ε-type single phase and the absorption coefficients of grown crystals have been improved according to the increase of applied Se vapor pressure during crystal growth.

Synthesis, structure, and characterization of a new promising nonlinear optical crystal: Cd5(BO3)3F

A nonlinear optical crystal cadmium fluoroborate (Cd5(BO3)3F) has been synthesized through high-temperature solid-state reactions. In the crystal structure, CdOnFm (n = 4, 5, 7; m = 0, 1, 2) distorted polyhedra interconnect via shared edges and corners to form a 3D framework with tunnels along the c axis. BO3 planar triangles lie approximately parallel in the (001) plane. The combination of triangular BO3 groups with π-conjugated systems and the d10 cation Cd2+ with polar displacement produces large SHG responses. The second harmonic generation (SHG) measurement shows that Cd5(BO3)3F possesses a large SHG response about four times that of KH2PO4 (KDP) and is phase-matchable in the visible region. In addition, it exhibits a wide transparent region ranging from UV to near IR, which suggests that the material is a promising NLO material.

Growth and nonlinear optical properties of BaAlBO_3F_2 crystal

BaAlBO3F2 (BABF), a newly developed nonlinear optical (NLO) crystal, was fully investigated for high-power harmonic generation of UV light. This was performed after successfully growing high-quality single crystals in the LiF–B2O3–NaF flux system. Thermal expansion, specific heat, transmittance spectrum, nonlinear optical coefficients, and laser damage threshold were measured. High-power NLO experiments were also conducted for what we believe to be the first time for BABF crystals. Because BABF is absolutely not hygroscopic, the appealing physical, chemical, optical, and NLO properties make BABF a promising NLO crystal for practical application in high-power UV light generation.

WAVEGUIDE STRUCTURES FOR GENERATION OF TERAHERTZ RADIATION BY ELECTRO-OPTICAL PROCESS IN GaAs AND ZuGeP<sub>2</sub> USING 1.55μm FIBER LASER PULSES

By discussing the basic schemes of the terahertz generation methods based on the 1550-nm ultrafast lasers briefly, GaAs and ZnGeP2 are likely to be promising nonlinear optical crystals for terahertz waves generation by using optical rectification process. However, the mismatches of velocities between the terahertz waves and optical pulses are so large that the phase-matching coherent lengths are quite short, for example, the coherent length of 0.7 mm for GaAs and 0.5 mm for ZnGeP2 at 2 THz around, respectively. That limited extremely the applications of these bulk excellent nonlinear optical crystals in terahertz regime. In this paper, we demonstrated theoretically that the dielectric planar waveguide could be used to enhance the coherent length of optical rectification process in THz regime. And for the first time, a dielectric planar THz waveguide that has potential applicable value in THz generation by optical rectification method was proposed. We predicted that the effective coherent length could be extended to 4 mm at 2 THz in a GaAs/ZnGeP2 dielectric planar waveguide during optical rectification process pumped by ultrafast optical pulses at wavelength of 1550 nm.

Influence of scattering centers on UV transmittance in Li2B4O7 single crystals and its origin

Nonlinear optical borate crystal has been attracted much attention as wavelength conversion device with development of ultra violet (UV) all solid-state laser systems. Li2B4O7 crystal is one of promising nonlinear optical crystals in UV region as well as piezoelectric substrate for SAW and BAW devices. In this paper, we have examined scatter center with submicron size, which is most effective defects, leading to the degradation of nonlinear optical devices in UV region. The scatter center is a void and the size distribution of scatter centers is revealed by the transparency measurement in UV region. From these experimental results, scatter free Li2B4O7 single crystals showing high transparency in UV region have been successfully grown by Czochralski (CZ) method with dry air flow.