Deep-ultraviolet Nonlinear Optical Materials Research Articles

Structure and Origin of the Second-Harmonic Generation Response of Nonlinear Optical Material Sr2Be2B2O7.

Sr2Be2B2O7 (SBBO) has long been considered as one of the most promising deep-ultraviolet nonlinear optical materials, but its crystal structure described by space group P6̅c2 in previous studies has remained questionable. On the basis of first-principles calculations coupled with the high-throughput crystal structure prediction method, we found three energetically favorable structures for SBBO with space groups Cm, Pm, and P6̅. These structures and a superstructure of space group Pm-S derived from the Cm structure were refined by the Rietveld method using the available powder X-ray diffraction data. These analyses show that the Pm-S structure is the best one, but its parent Cm structure is almost equally good and has the advantage of having higher symmetry. Via atom response theory analysis, we resolved the cause for the second-harmonic generation (SHG) responses of SBBO at the atomic and orbital level to elucidate the importance of local inversion symmetry in reducing the SHG response.

Coordination-Directed Structural Modulation and Design of Deep-Ultraviolet Nonlinear Optical Materials

The exploration of new nonlinear optical (NLO) materials which can realize the balance between deep-ultraviolet (UV) transparency and large NLO response is still urgently needed owing to their abil...

Deep‐Ultraviolet Nonlinear‐Optical van‐der‐Waals Beryllium Borates**

AbstractVan‐der‐Waals (vdW) deep‐ultraviolet (DUV) nonlinear‐optical (NLO) materials hold great potential to extend DUV NLO applications to two dimensions, but they are rare in nature. In this study, we propose a design principle to realize vdW DUV NLO materials via structural evolution from the non‐vdW (BO3)‐(BeO3F) layers in KBe2BO3F2 (KBBF) to the vdW (BO3)‐(BeO4H) layers in berborite Be2BO5H3 (BBH) and the vdW (BO4)‐(BeO4) layers in beryllium metaborate BeB2O4 (BEBO). Based on first‐principles calculations, the fundamental NLO properties of BBH and BEBO demonstrate that a balanced DUV NLO performance can be achieved in these two systems. Importantly, BBH, a layered material existing in nature, can achieve an available DUV phase‐matched output with strong second harmonic generation (SHG) for 177.3/193.7 nm DUV lasers, which is almost identical to that of KBBF. Remarkably, BEBO shows an excellent DUV SHG capacity and an even shorter phase‐matching wavelength than KBBF. Therefore, the newly discovered vdW BBH and BEBO, once verified by experiments, could provide an ideal platform to study DUV NLO effects in three dimensions and two dimensions.

LiB2O3F: A Beryllium-Free Deep-Ultraviolet Nonlinear Optical Material Designed Based on a Boron-Rich Strategy

LiB₂O₃F: A Beryllium-Free Deep-Ultraviolet Nonlinear Optical Material Designed Based on a Boron-Rich Strategy

Two deep-ultraviolet nonlinear optical barium borates framework: Alkali metal enhances the second-harmonic generation response

Two non-centrosymmetric barium borates with acs-type net, namely Ba3 [B9O16][B(OH)4]·2H2O (1) and NaBa3(OH)[B9O16][B(OH)4] (2) have been synthesized under hydrothermal conditions. Compound 1 is type-I phase matchable with second-harmonic generation (SHG) response of approximately 1.6 times than that of KDP (KH2PO4). After Na+ cation has been successfully introduced into the oxoboron cluster backbone, compound 2 displays a larger SHG response about approximately 2.0 times of KDP. The calculations show that the large local dipole moments of distorted NaO7 polyhedrons make 2 exhibits a relatively larger SHG response. The ultraviolet–visible (UV–Vis) diffuse reflectance spectra show that both 1 and 2 have a wide transparency range with UV cutoff edge below 200 ​nm. These properties reveal that the introduction of different size and charge alkali metal on the basis of alkaline earth metal borate is beneficial to obtain a promising deep-ultraviolet nonlinear optical (NLO) material with a larger SHG response.

Struvite-type AMgPO4·6H2O (A = NH4, K): Two Natural Deep-Ultraviolet Transparent Nonlinear Optical Crystals.

Deep-ultraviolet (DUV) nonlinear optical (NLO) materials play vital roles in diverse fields. Unfortunately, only the KBe2BO3F2 crystal has found commercial applications so far. Therefore, the discovery of new DUV NLO crystals is still urgent. As we all know, digging into the properties of existing crystals is also an effective way to obtain new NLO crystals. Herein, two natural asymmetric orthophosphates AMgPO4·6H2O (A = NH4, K) are proposed. Although their structures and some properties such as infrared spectra, thermal properties, and dielectric properties have been previously characterized, their NLO properties have not been reported. Thus, in this work, these two natural DUV transparent orthophosphates NH4MgPO4·6H2O (NMP) and KMgPO4·6H2O (KMP) were successfully acquired by a simple slow evaporation method. The single-crystal X-ray diffraction data indicate that NMP and KMP are isomorphic and that both belong to the Pmn21 space group of the orthorhombic system. Remarkably, NMP and KMP possess short cutoff edges below 190 nm, and their second-harmonic generation (SHG) efficiencies are 0.62 and 0.80 times that of KH2PO4(KDP), respectively; furthermore, they can achieve type-I phase matching at 1064 nm.

Prediction of Novel van der Waals Boron Oxides with Superior Deep-Ultraviolet Nonlinear Optical Performance.

Deep-ultraviolet nonlinear optical (DUV NLO) materials are attracting increasing attention because of their structural diversity and complexity. Using the two-dimensional (2D) crystal structure prediction method combined with the first-principles calculations, here we propose layered 18-membered-ring (18MR) boron oxide B2 O3 polymorphs as high-performance NLO materials. 18MR-B2 O3 with the AA and AB stackings are potential DUV NLO materials. The superior performing 18MR-B2 O3 AB has an unprecedentedly high second harmonic generation coefficient of 1.63 pm V-1 , the largest among the DUV NLO materials, three times larger than that of the advanced DUV NLO material KBe2 BO3 F2 and comparable to that of β-BaB2 O4 . Its unusually large birefringence of 0.196 at 400 nm guarantees the phase-matching wavelength λPM to reach this material's extreme absorption edge of ≈154 nm.

Computationally assisted multistage design and prediction driving the discovery of deep-ultraviolet nonlinear optical materials

The property-driven materials multistage design process from analytical method development, functional groups, module to functional layer analysis and structural prediction is described to explore new deep-ultraviolet nonlinear optical materials.

Deep-ultraviolet nonlinear optical crystals by design: A computer-aided modeling blueprint from first principles

Deep-ultraviolet (DUV) nonlinear optical (NLO) crystal is indispensable in current DUV all-solid-state laser technology, which is the key device to generate DUV light by frequency conversion. Due to stringent criteria, DUV NLO crystals are scarce and their discovery faces a big challenge. Although KBe2BO3F2 (KBBF) is already excellent for current uses, the development of DUV science requires the materials with shorter output wavelengths and larger NLO effects, so as to meet the needs of DUV lasers with higher precision and higher power. Therefore, how to efficiently design DUV NLO materials has always been the core issue in NLO materials science. Looking back on the development of NLO materials, it turns out that theoretical modeling and simulation is an effective and efficient method, not only for mechanism understandings, but also for experimental exploration. In this article, in order to accelerate the process of DUV materials discovery, we summarize and propose a powerful computer-aided modeling system and design blueprint that can be used to evaluate the DUV NLO performance in a faster way than pure experiments. With this in hand, we enrich the understanding of NLO structure-property correlation, and systematically prospect the DUV NLO properties on the basis of many existing and designed structures according to different structural types and chemical compositions. Seven novel structures are predicted for the first time to exhibit potential DUV NLO capabilities. All the results enable us to believe that the computer-aided modeling blueprint will play an important role in the exploration of new DUV NLO crystals.

Designing Silicates as Deep-UV Nonlinear Optical (NLO) Materials using Edge-Sharing Tetrahedra.

Discovering new deep-ultraviolet (DUV) nonlinear optical (NLO) materials is currently a great challenge. The reported DUV NLO materials are almost exclusively borates or phosphates. Silicates-the largest constituent of the earth's crust-are excluded owing to their weak second harmonic generation (SHG) response. We report a silicate, Li2 BaSiO4 , with edge-sharing LiO4 -SiO4 tetrahedra that achieves the balance between a short UV absorption edge, below 190 nm, and a large SHG response, 2.8×KDP. The SHG intensity is the largest for silicates without second-order Jahn-Teller cations, and exceeds that of non-isomorphic Li2 SrSiO4 by more than an order of magnitude. As such Li2 BaSiO4 may be seen as a promising DUV-UV NLO material. This research indicates that edge-sharing tetrahedra is a new design parameter for discovering new DUV NLO materials.

Designing Silicates as Deep‐UV Nonlinear Optical (NLO) Materials using Edge‐Sharing Tetrahedra

AbstractDiscovering new deep‐ultraviolet (DUV) nonlinear optical (NLO) materials is currently a great challenge. The reported DUV NLO materials are almost exclusively borates or phosphates. Silicates—the largest constituent of the earth's crust—are excluded owing to their weak second harmonic generation (SHG) response. We report a silicate, Li2BaSiO4, with edge‐sharing LiO4–SiO4 tetrahedra that achieves the balance between a short UV absorption edge, below 190 nm, and a large SHG response, 2.8×KDP. The SHG intensity is the largest for silicates without second‐order Jahn–Teller cations, and exceeds that of non‐isomorphic Li2SrSiO4 by more than an order of magnitude. As such Li2BaSiO4 may be seen as a promising DUV‐UV NLO material. This research indicates that edge‐sharing tetrahedra is a new design parameter for discovering new DUV NLO materials.

Shilie Pan.

"My motto is 'Continual dropping wears away the stone'. If I could be a piece of lab equipment, I would be a single-crystal X-ray diffractometer …" Find out more about Shilie Pan in his Author Profile.

A Promising Fluorooxoborate Framework with Flexibile Capability for Diverse Cations to Enhance the Second Harmonic Generation.

Fluorooxoborates as potential deep ultraviolet (DUV) nonlinear optical (NLO) materials have exhibited diverse structures and NLO properties with metal cationic changes. Herein, the general mechanisms of metal cations on band gaps and optical properties in a series of typical fluorooxoborates have been clarified. It reveals that the framework of the emblematic 18-membered ring oxyfluorides has the flexibility of being able to contain different cations spanning from alkali to d10 metals by investigating the stability of the artificial CdB5 O7 F3 structure. Besides, introducing d10 metal cations can enhance the second harmonic generation (3.1×KH2 PO4 (KDP), d36 =0.39 pm V-1 ) and also keep a DUV spectral transparency (Eg >6.2 eV). Thus, the d10 -containing fluorooxoborate exhibits a great potential to be a new DUV optical material for nonlinear light-matter interactions.

CsAlB3O6F: a beryllium-free deep-ultraviolet nonlinear optical material with enhanced thermal stability.

The design of new beryllium-free deep-ultraviolet nonlinear optical materials is important but challenging. Here, we describe a new strategy to search for such materials based on rational selection of fundamental structural units. By combining asymmetric AlO3F tetrahedra and π-conjugated B3O6 rings, a new aluminum borate fluoride, CsAlB3O6F was obtained. It exhibits excellent linear and nonlinear optical properties including a high optical transmittance with a cut-off edge shorter than 190 nm, large second harmonic generation intensities (2.0× KH2PO4, KDP), and suitable birefringence for phase-matching under 200 nm. It also has good thermal stability and can be synthesized easily in an open system.

Giant enhancement of the nonlinear optical properties of [2.2]paracyclophanes by an donor-bridge-acceptor

Recently, the modulating the charge transfer of the donor-S-acceptor (DSA) has been proven as an appropriate method to increase the static first hyperpolarizability of the molecule. In this work, we employ the extended π-conjugated bridge to further explore the charge transfer effect on the nonlinear optical response, where (CHCH)nNH2 and (CHCH)nNO2 are served as an donor group and acceptor group, respectively. Electrostatic potentials on the molecular surface of all molecules indicate that charge transfer is found from donor group to acceptor group, which indicates that these molecules may be excellent nonlinear optical materials. The calculations proves that these molecules exhibit large first hyperpolarizability in the range of 3485−46199 au. Compared with short chain, long chain brings these molecules the large first hyperpolarizability, which are 146199 au for n = 4. Moreover, the ultraviolet-visible-infrared indicate that the molecule is transparent in the deep-ultraviolet, which may be regarded as a new candidate for deep ultraviolet nonlinear optical materials. The transition can give reasons for the change in the first hyperpolarizability of these molecules. We hope that this paper can provide new insights for the design of nonlinear optical materials.

β-Ba(PO3)2 with DUV cut-off edge and large birefringence

Phosphates are another new family of exploring deep-ultraviolet nonlinear optical materials. As one material, the simpler the composition is the more favorable synthesis and application is. In this work, a simple alkaline earth metal phosphate β-Ba(PO3)2 was synthesized by high temperature solid phase method. It is worth mentioning that it has short cut-off edge (<190 nm) and relatively large birefringence (Δn = 0.032 @ 1064 nm) in phosphates and the optical anisotropy and birefringence can be enhanced by optimizing the basic anion arrangement. Combining with theoretical analysis, the relationship between structure and performance is further elaborated. In additional, thermal properties, linear optical and nonlinear optical properties for β-Ba(PO3)2 were also investigated.

An Effective and Facile Method To Prepare Monofluorophosphates Overcoming the Common Difficulty of Loss of Fluorine and Serious Corrosion: 12 Examples and Their Characterizations and Properties

Monofluorophosphate, being an important industry chemical, such as an additive in toothpaste, has been recently recognized as a new source of excellent deep-ultraviolet nonlinear optical materials ...

Prediction of Fluorooxoborates with Colossal Second Harmonic Generation (SHG) Coefficients and Extremely Wide Band Gaps: Towards Modulating Properties by Tuning the BO3 /BO3 F Ratio in Layers.

Fluorooxoborates have inspired investigations of deep-ultraviolet (DUV) nonlinear optical (NLO) materials that can meet the multiple criteria. Herein, five stable structures with the composition of BaB2 O3 F2 (I-V) are discovered using the ab initio evolutionary algorithm. Among them, BaB2 O3 F2 -I has been synthesized experimentally and confirms the reliability of the method. All of the predicted structures possess extremely wide band gaps (8.1-9.0 eV). Moreover, four new structures exhibit giant second harmonic generation (SHG) coefficients (>3×KDP, d36 =0.39 pm V-1 ). A novel type of the [BOF] layer with BO3 :BO3 F ratio of [1:1] is found in BaB2 O3 F2 -II and BaB2 O3 F2 -III. While BaB2 O3 F2 -IV and BaB2 O3 F2 -V are solely composed of the BO3 F group and have colossal SHG coefficients (ca. 4×KDP). It gives the direct evidence that the BO3 F group could generate strong SHG effect. Most importantly, the influences of BO3 :BO3 F ratio and their number density on band gap, birefringence and SHG effects are investigated.

Poly(difluorophosphazene) as the First Deep-Ultraviolet Nonlinear Optical Polymer: A First-Principles Prediction.

A novel concept to obtain the deep-ultraviolet (DUV) nonlinear optical (NLO) materials is proposed based on the assembling of one-dimensional (1D) polar motifs into quasi-1D polymer patterns. Based on the first-principles calculations, we have successfully discovered an excellent DUV NLO polymer, i.e., poly(difluorophosphazene), with the chemical formula of (PNF2 )n . Calculations reveal that PNF2 has a larger band gap, a stronger second harmonic generation effect, a larger birefringence, and a shorter phase-matching cutoff than KBe2 BO3 F2 . These findings not only demonstrate that the PNF2 is the first reported DUV NLO polymer, but also could open a new direction to discover novel DUV NLO materials in polymer systems.

Poly(difluorophosphazene) as the First Deep‐Ultraviolet Nonlinear Optical Polymer: A First‐Principles Prediction

AbstractA novel concept to obtain the deep‐ultraviolet (DUV) nonlinear optical (NLO) materials is proposed based on the assembling of one‐dimensional (1D) polar motifs into quasi‐1D polymer patterns. Based on the first‐principles calculations, we have successfully discovered an excellent DUV NLO polymer, i.e., poly(difluorophosphazene), with the chemical formula of (PNF2)n. Calculations reveal that PNF2 has a larger band gap, a stronger second harmonic generation effect, a larger birefringence, and a shorter phase‐matching cutoff than KBe2BO3F2. These findings not only demonstrate that the PNF2 is the first reported DUV NLO polymer, but also could open a new direction to discover novel DUV NLO materials in polymer systems.