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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

First principles crystal engineering of nonlinear optical materials. I. Prototypical case of urea

The crystalline materials with nonlinear optical (NLO) properties are critically important for several technological applications, including nanophotonic and second harmonic generation devices. Urea is often considered to be a standard NLO material, due to the combination of non-centrosymmetric crystal packing and capacity for intramolecular charge transfer. Various approaches to crystal engineering of non-centrosymmetric molecular materials were reported in the literature. Here we propose using global lattice energy minimization to predict the crystal packing from the first principles. We developed a methodology that includes the following: (1) parameter derivation for polarizable force field AMOEBA; (2) local minimizations of crystal structures with these parameters, combined with the evolutionary algorithm for a global minimum search, implemented in program USPEX; (3) filtering out duplicate polymorphs produced; (4) reoptimization and final ranking based on density functional theory (DFT) with many-body dispersion (MBD) correction; and (5) prediction of the second-order susceptibility tensor by finite field approach. This methodology was applied to predict virtual urea polymorphs. After filtering based on packing similarity, only two distinct packing modes were predicted: one experimental and one hypothetical. DFT + MBD ranking established non-centrosymmetric crystal packing as the global minimum, in agreement with the experiment. Finite field approach was used to predict nonlinear susceptibility, and H-bonding was found to account for a 2.5-fold increase in molecular hyperpolarizability to the bulk value.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Na{sub 2}Ge{sub 2}Se{sub 5}: A highly nonlinear optical material

We report an integrated experimental and theoretical study of the two-dimensional polar selenogermanate compound Na{sub 2}Ge{sub 2}Se{sub 5}, which exhibits strong nonlinear optical (NLO) second harmonic generation response in the visible and infrared region. The compound is type-I phase-matchable with a large SHG coefficient {chi}{sup (2)} Almost-Equal-To 290 pm V{sup -1}, which is the second highest among the phase-matchable NLO materials. It also performs as an NLO frequency mixer to produce radiation via difference frequency generation. The compound is optically transparent from the visible (0.521 {mu}m) to the far IR (18.2 {mu}m) and melts congruently. Ab initio density functional theory band structure calculations show that the unusually large second-order optical nonlinearity is attributed to the two-dimensional character of the crystal structure. Raman, IR and optical absorption spectroscopy, differential thermal analysis, NLO properties of derivatives of Na{sub 2}Ge{sub 2}Se{sub 4.55}Te{sub 0.45} and Na{sub 2}Ge{sub 1.64}Sn{sub 0.36}Se{sub 5} and thermal expansion behavior studies are also reported. - Graphical Abstract: Na{sub 2}Ge{sub 2}Se{sub 5} is a new second-order nonlinear optical material for IR applications. It is type-I phase-matchable with a large SHG coefficient {chi}{sup (2)} Almost-Equal-To 290 pm V{sup -1}, which is the second largest among the phase-matchable NLO materials. Highlights: Black-Right-Pointing-Pointer Na{sub 2}Ge{sub 2}Se{sub 5} is a new second-order nonlinear optical material for IR applications. Black-Right-Pointing-Pointer It is type-I phase-matchable. Black-Right-Pointing-Pointer Its SHG coefficient {chi}{sup (2)} Almost-Equal-To 290 pm V{sup -1} is the second largest among the phase-matchable NLO materials. Black-Right-Pointing-Pointer Its DFG performance allows the development of a multiple IR frequency source with tunability. Black-Right-Pointing-Pointer Ab initio density functional theory band structure calculations show that the unusually large second-order optical nonlinearity is attributed to the 2-D character of the crystal structure.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Beryllium-Free β-Rb 2 Al 2 B 2 O 7 as a Possible Deep-Ultraviolet Nonlinear Optical Material Replacement for KBe 2 BO 3 F 2

A new beryllium-free deep-ultraviolet (DUV) nonlinear optical (NLO) material, β-Rb 2 Al 2 B 2 O 7 (β-RABO), has been synthesized and characterized. The chiral nonpolar acentric material shows second-harmonic generation (SHG) activity at both 1064 and 532 nm with efficiencies of 2×KH 2 PO 4 and 0.4×β-BaB 2 O 4 , respectively, and exhibits a short absorption edge below 200 nm. β-Rb 2 Al 2 B 2 O 7 has a three-dimensional structure of corner-shared Al(BO 3 ) 3 O polyhedra. The discovery of β-RABO demonstrates that through careful synthesis and characterization, replacement of KBe 2 BO 3 F 2 (KBBF) by a Be-free DUV NLO material is possible.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Beryllium‐Free β‐Rb 2 Al 2 B 2 O 7 as a Possible Deep‐Ultraviolet Nonlinear Optical Material Replacement for KBe 2 BO 3 F 2

Abstract A new beryllium‐free deep‐ultraviolet (DUV) nonlinear optical (NLO) material, β‐Rb 2 Al 2 B 2 O 7 (β‐RABO), has been synthesized and characterized. The chiral nonpolar acentric material shows second‐harmonic generation (SHG) activity at both 1064 and 532 nm with efficiencies of 2×KH 2 PO 4 and 0.4×β‐BaB 2 O 4 , respectively, and exhibits a short absorption edge below 200 nm. β‐Rb 2 Al 2 B 2 O 7 has a three‐dimensional structure of corner‐shared Al(BO 3 ) 3 O polyhedra. The discovery of β‐RABO shows that through careful synthesis and characterization, replacement of KBe 2 BO 3 F 2 (KBBF) by a Be‐free DUV NLO material is possible.

Tran, T. Thao↗
DOE OSTI2012

Crystal structure, optical and thermal studies of a new organic nonlinear optical material: L-Histidinium maleate 1.5-hydrate

Highlights: ► L-Histidinium maleate 1.5-hydrate, a new organic crystal has been grown for the first time. ► The crystal structure is reported for the first time (CCDC 845975). ► The crystal belongs to monoclinic system with space group P2{sub 1}, Z = 4, a = 11.4656(7) Å, b = 8.0530(5) Å, c = 14.9705(9) Å and β = 101.657(2)°. ► The optical absorption study substantiates the complete transparency of the crystal. ► Kurtz powder SHG test confirms the nonlinear property of the crystal. -- Abstract: A new organic nonlinear optical material L-histidinium maleate 1.5-hydrate (LHM) with the molecular formula C{sub 10}H{sub 16}N{sub 3}O{sub 7.5} has been successfully synthesized from aqueous solution by slow solvent evaporation method. The structural characterization of the grown crystal was carried out by single crystal X-ray diffraction at 293(2) K. In the crystal, molecules are linked through inter and intramolecular N-H⋯O and O-H⋯O hydrogen bonds, generate edge fused ring motif. The hydrogen bonded motifs are linked to each other to form a three dimensional network. The FT-IR spectroscopy was used to identify the functional groups of the synthesized compound. The optical behavior of the grown crystal was examined by UV–visible spectral analysis, which shows that the optical absorption is almost negligible in the wavelength range 280–1300 nm. The nonlinear optical property was confirmed by the powder technique of Kurtz and Perry. The thermal behavior of the grown crystal was analyzed by thermogravimetric analysis.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Generation of ultra-short THz pulses in new optical nonlinear materials based on organic polymers

Using the method of optical rectification of femtosecond laser pulses, we report the generation of short (a few field cycles) terahertz pulses in the samples of films based on polyimides with covalently bound chromophore molecules of DR type. The spectral width of the produced pulses is limited by the pump pulse duration. The quadratic nonlinear optical properties are imparted to the films in the process of their fabrication by orienting the chromophore molecules in the external electric field of the applied electrodes having an original configuration. The samples are compared with the ZnTe crystal. Using the methods of coherent spectroscopy, their transmission and refractive index dispersion spectra are investigated in the frequency range 0.5 – 2.6 THz. The studied polymer composition is promising for the application in coherent spectrometers both for increasing the working spectral range without dips and for improving the spatial resolution in the near-field terahertz spectroscopy. (nonlinear optical phenomena)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Nonlinear encoding in diffractive information processing using linear optical materials

Nonlinear encoding of optical information can be achieved using various forms of data representation. Here, we analyze the performances of different nonlinear information encoding strategies that can be employed in diffractive optical processors based on linear materials and shed light on their utility and performance gaps compared to the state-of-the-art digital deep neural networks. For a comprehensive evaluation, we used different datasets to compare the statistical inference performance of simpler-to-implement nonlinear encoding strategies that involve, e.g., phase encoding, against data repetition-based nonlinear encoding strategies. We show that data repetition within a diffractive volume (e.g., through an optical cavity or cascaded introduction of the input data) causes the loss of the universal linear transformation capability of a diffractive optical processor. Therefore, data repetition-based diffractive blocks cannot provide optical analogs to fully connected or convolutional layers commonly employed in digital neural networks. However, they can still be effectively trained for specific inference tasks and achieve enhanced accuracy, benefiting from the nonlinear encoding of the input information. Our results also reveal that phase encoding of input information without data repetition provides a simpler nonlinear encoding strategy with comparable statistical inference accuracy to data repetition-based diffractive processors. Our analyses and conclusions would be of broad interest to explore the push-pull relationship between linear material-based diffractive optical systems and nonlinear encoding strategies in visual information processors.

42 ENGINEERING↗
DOE OSTI2018

Toward First-Principles Design of Organic Nonlinear Optical Materials: Crystal Structure Prediction and Halogen Bonding Impact on Hyperpolarizabilities of 2-Iodo-3-hydroxypyridine

Computational methods can potentially accelerate development of more efficient organic materials for second harmonic generation. Here, we test the method that includes the evolutionary algorithm for predicting crystal structure and prognosis of nonlinear optical properties based on the predicted structure. For this test, we selected 2-iodo-3-hydroxypyridine, which exhibits second harmonic generation intensity comparable to that of urea. We performed global minimization of the lattice energy and found the experimental structure when many-body dispersion correction is added to the density functional theory values. We analyzed geometric preferences of the halogen bonding in predicted virtual polymorphs. We also found linear correlation between the lengths of the iodine–iodine halogen bonds and calculated second order susceptibilities.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Effects of structure distortion on optical phonon properties of crystalline beta-BaTeMo{sub 2}O{sub 9}—A novel nonlinear optical material: Infrared and Raman spectra as well as first-principles calculations

The infrared dielectric property of monoclinic BaTeMo{sub 2}O{sub 9} single crystals is studied by polarized IR reflectance spectra from 20 to 1800 cm{sup −1}. Based on the modified Lorentz model, the frequencies, strengths, and dampings of TO modes as well as the orientations of the dipole momenta are determined, agreeing well with Raman spectra and results from First-principles calculation. The observed modes are visually assigned to the specific atoms' motions in the primitive cell based on the theory calculations. A large shift of the internal modes of the anion groups relative to free anion co-ordination polyhedra is observed, which can be used to indicate the distortions of co-ordination polyhedra related to the nonlinear optical properties. Further, the experimental results of the strengths of the oscillators support the elimination and splitting of degenerate modes in free regular polyhedrons. These results offer a way to evaluate the nonlinear optical properties by use of traditional IR reflectivity spectra.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Semiorganic nonlinear optical material: Crystal growth, structure and optical properties of NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2}

Graphical abstract: - Highlights: • Semiorganic NLO material NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} has been grown with sizes up to 8 × 5 × 2 mm{sup 3}. • It crystallizes in the noncentrosymmetric Monoclinic space group P2. • Thermal analysis demonstrated NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} are thermally stable up to 280. • NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} has an absorption edge about 220 nm in the UV region. • It exhibits a NLO efficiency of about two times that of KDP (KH{sub 2}PO{sub 4}) standard. - Abstract: Single crystal of the semiorganic NLO material NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} has been grown with sizes up to 8 × 5 × 2 mm{sup 3} by the slow evaporation method. The crystal structure of this compound was determined by single crystal X-ray diffraction. It crystallizes in the Monoclinic space group P2 with lattice parameters a = 5.4045(11) Å, b = 11.692(2) Å, c = 9.4773(19) Å and Z = 2. Thermal analysis demonstrated NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} are thermally stable up to 280 °C. NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} exhibits an absorption edge about 220 nm in the UV region. The powder second-harmonic generation (SHG) measurement performed on the ground crystal indicates that it has a NLO efficiency of about 2 times that of KDP (KH{sub 2}PO{sub 4}) standard. In addition, the origin of stronger SHG effect was discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Ba 2 Si 3 P 6 : 1D Nonlinear Optical Material with Thermal Barrier Chains

A novel barium silicon phosphide was synthesized and characterized. Ba 2 Si 3 P 6 crystallizes in the noncentrosymmetric space group Pna2 1 (No. 33) and exhibits a unique bonding connectivity in the Si–P polyanion not found in other compounds. The crystal structure is composed of SiP4 tetrahedra connected into one-dimensional double-tetrahedra chains through corner sharing, edge sharing, and covalent P–P bonds. Chains are surrounded by Ba cations to achieve an electron balance. The novel compound exhibits semiconducting properties with a calculated bandgap of 1.6 eV and experimental optical bandgap of 1.88 eV. The complex pseudo-one-dimensional structure manifests itself in the transport and optical properties of Ba 2 Si 3 P 6 , demonstrating ultralow thermal conductivity (0.56 W m –1 K –1 at 300 K), promising second harmonic generation signal (0.9 × AgGaS 2 ), as well as high laser damage threshold (1.6 × AgGaS 2 , 48.5 MW/cm 2 ) when compared to the benchmark material AgGaS 2 . Differential scanning calorimetry reveals that Ba 2 Si 3 P 6 melts congruently at 1373 K, suggesting that large single crystal growth may be possible.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Lanthanide thioborates, an emerging class of nonlinear optical materials, efficiently synthesized using the boron–chalcogen mixture method

Here, the Boron–Chalcogen Mixture method was used to obtain single crystals of the previously extremely difficult to synthesize lanthanide orthothioborates to investigate their structures and their structurally connected optical behavior, such as second harmonic generation. Using a combined halide and polychalcogenide flux, the BCM method yielded single crystals of LnBS 3 (Ln = La, Ce, Pr, Nd), which are isostructural and crystallize in the non-centrosymmetric space group, Pna2 1 . Second harmonic generation measurements confirmed the expectation that LaBS 3 would exhibit a strong SHG response, measured at 1.5 × KDP.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Crystal Growth and Characterization of Epitaxial Layers of Laser and Nonlinear Optical Materials for Thin-Disk and Waveguide laser applications

This paper summarizes the main results we obtained in our laboratories in relation with crystalline layers obtained by liquid phase epitaxial growth of lanthanide doped KLu(WO{sub 4}){sub 2} and Nb:RbTiOPO{sub 4} grown on KLu(WO{sub 4}){sub 2} and RbTiOPO{sub 4} substrates, respectively. Macroscopic defect free epitaxial layers were grown and characterized in terms of their compositional homogeneity, structural stress in the layer/substrate interface and laser and waveguiding performances.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Enhancement of second-order optical nonlinearities and nanoscale periodic domain patterning in ferroelectric boron-substituted aluminum nitride thin films

The discovery and development of CMOS-compatible, nonlinear optical materials is essential to produce integrated photonic devices with advanced functionalities. AlN is a strong candidate for on-chip device demonstration due to its intrinsic second-order optical nonlinearities, large bandgap, and well-established fabrication techniques. However, AlN is not easily phase matched for the largest coefficient d 33 ; the coefficients that could potentially be dispersion phase-matched, d 31 and d 15 , have weak nonlinearities. This work investigates ferroelectric Al 1-x B x N (x = 0 to 0.11) for viability as a large bandgap nonlinear optical material with unique suitability towards ultraviolet light generation using second harmonic generation. The linear and nonlinear optical properties are characterized accounting for material anisotropy. With increasing B concentration, a large enhancement from near negligible values to d 31 = 0.9 ± 0.1 pm/V and d 15 = 1.2 ± 0.1 pm/V is observed. This compares favorably to other large bandgap materials like β-Ba(BO 2 ) 2 , where the largest nonlinear coefficient is d 22 ~ 2.3 pm/V at 800 nm. This is accompanied by a change in the bandgap from 6.1 eV to 5.8 eV as B substitution goes from 0 to 11%. A periodically poled, quasi-phase-matched ferroelectric domain pattern with 400 nm domain size and a wall roughness of <16 nm is demonstrated.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Deterministic modeling of hybrid nonlinear effects in epsilon-near-zero thin films

In nonlinear optics, significant effort is concentrated on improving the strength and efficiency of interactions; however, experimentally investigating nonlinear materials is a complex, time-consuming, and costly investment. Moreover, it is often challenging to isolate, study, and optimize material parameters in an experiment due to complexities in the growth process. Recently, epsilon-near-zero materials have received a great deal of attention as promising nonlinear optical materials, but like many up-and-coming materials, the ability to explore and optimize their properties has been challenging. Here, we establish a framework to rapidly evaluate the performance of nonlinear epsilon-near-zero materials for both inter- and intraband effects in silico, requiring only an energy-momentum (E-k) diagram, linear optical properties, and experimental conditions. Measured nonlinear reflection and transmission in gallium-doped zinc oxide films are compared to the numerical framework for both intra- and interband excitation to verify accuracy across wavelength and irradiance while two figures of merit (FoMs) are introduced to quickly evaluate the performance of films without a full numerical framework. This capability is used to predict the performance of highly doped gallium nitride, cadmium oxide, zinc oxide, and indium tin oxide films, and efficient intra- and interband operation conditions are identified. Through this numerical framework and the FoMs, the exploration of unstudied epsilon-near-zero materials is enabled without the need for a nonlinear experiment, thereby accelerating the search for more efficient nonlinear materials and excitation conditions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Fabrication and characterization of electrospun single-crystal lead manganese borate nanofibers

Highlights: • Single crystal PbMnBO4 nanofibers were successfully fabricated by electrospinning process. • The PbMnBO4 nanofibers synthesized for the first time and unprecedented in the literature. • Characterization of PbMnBO{sub 4} nanofibers in mineralogical, optical and thermal properties was revealed. • The nanofibers exhibit single crystalline features with an average size between 120 and 250 nm. • These nanofibers can be used in optic or photonic fields as a flexible sensor due to its nonlinear and ferromagnetic properties. - Abstract: Anhydrous borate compounds are important materials in optical applications as nonlinear optical materials (NLO), due to the presence of structural B{sub x}O{sub y} subunits. Herein, lead manganese borate (PbMnBO{sub 4}) nanofibers have been firstly fabricated via a facile approach using a simple and inexpensive electrospinning technique. All of the synthesized samples were analyzed with X-Ray Diffractometer (XRD), Transmission Electron Microscope (TEM), Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR), and Ultraviolet-visible Spectroscopy (UV–vis) method. In addition, they were thermally analyzed with Thermal Gravimetric and Differential Thermal Analyzer and TG-DTA diagrams were discussed in detail. All of the characterization results showed that the obtained PbMnBO{sub 4} nanostructures have nanofiber structures and good crystalline features. PbMnBO{sub 4} nanofiber synthesized for the first time and unprecedented in the literature is promising absorber materials for nonlinear optic applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗