Mechanism for linear and nonlinear optical effects in LiB3O5, CsB3O5, and CsLiB6O10 crystals

[[abstract]]Electronic structure calculations of LiB3O5, CsB3O5, and CsLiB6O10 crystals from first principles are performed based on a plane-wave pseudopotential method. The static second-harmonic generation (SHG) coefficients are calculated at the independent-particle level with a formalism improved by our group and co-workers [Phys. Rev. B 60, 13 380 (1999)]. A real-space atom-cutting method is adopted to analyze the respective contributions of the cation and anionic groups to optical response. The calculated refractive indices and SHG coefficients are in good agreement with the experimental values. On the basis of these calculations, the influence of the cations on the band gaps and the optical responses is evaluated. The results show that with the increase of their radius their contributions to SHG become slightly more pronounced.[[incitationindex]]SCI[[booktype]]紙本[[booktype]]電子

Comparative investigations of the crystal structure and photoluminescence property of eulytite-type Ba3Eu(PO4)3 and Sr3Eu(PO4)3

In this study, the Ba3Eu(PO4)3 and Sr3Eu(PO4)3 compounds were synthesized and the crystal structures were determined for the first time by Rietveld refinement using powder X-ray diffraction (XRD) patterns. Ba3Eu-(PO4)3 crystallizes in cubic space group I4¯3d, with cell parameters of a = 10.47996(9) Å, V = 1151.01(3) Å3 and Z = 4; Ba2+ and Eu3+ occupy the same site with partial occupancies of 3/4 and 1/4, respectively. Besides, in this structure, there exists two distorted kinds of the PO4 polyhedra orientation. Sr3Eu(PO4)3 is isostructural to Ba3Eu(PO4)3 and has much smaller cell parameters of a = 10.1203(2) Å, V = 1036.52(5) Å3. The bandgaps of Ba3Eu(PO4)3 and Sr3Eu(PO4)3 are determined to be 4.091 eV and 3.987 eV, respectively, based on the UV–Vis diffuse reflectance spectra. The photoluminescence measurements reveal that, upon 396 nm n-UV light excitation, Ba3Eu(PO4)3 and Sr3Eu(PO4)3 exhibit orange-red emission with two main peaks at 596 nm and prevailing 613 nm, corresponding to the 5D0 → 7F1 and 5D0 → 7F2 transitions of Eu3+, respectively. The dynamic disordering in the crystal structures contributes to the broadening of the luminescence spectra. The electronic structure of the hosphates was calculated by the first-principles method. The analysis elucidats that the band structures are mainly governed by the orbits of phosphorus, oxygen and europium, and the sharp peaks of the europium f-orbit occur at the top of the valence bands

Strong SHG Responses in a Beryllium-Free Deep-UV-Transparent Hydroxyborate via Covalent Bond Modification

Deep-ultraviolet (deep-UV) nonlinear optical (NLO) crystals are key materials in creating tunable deep-UV lasers for frequency conversion technology. However, practical application of the sole usable crystal, KBe2BO3F2, has been hindered by the high toxicity of beryllium and its layering tendency in crystal growth. Herein, we report a beryllium-free deep-UV NLO material NaSr3(OH)(B9O16)[B(OH)4] (NSBOH), synthesized by a covalent bond modification strategy under hydrothermal conditions. Moisture-stable NSBOH exhibits strong second-harmonic generation (SHG) at 1064 nm (3.3 × KH2PO4) and 532 nm (0.55 × β-BaB2O4), both amongst the largest powder SHG responses for a deep-UV borate, with good phase-matchability and a short wavelength cutoff edge (below 190 nm). NSBOH possesses a 3D covalent anionic [B9O19]∞ honeycomb-like framework with no layering. The Sr2+ and Na+ ions, residing in the cavities of the anionic framework, act as templates for the assembly and favorable alignment of NLO-active groups, resulting in an optimal balance between strong SHG activities and wide UV transparency. These merits indicate NSBOH is a very attractive candidate for deep-UV NLO applications.This research was financially supported by the National Natural Science Foundation of China (No. 51432006), the Ministry of Education of China for the Changjiang Innovation Research Team (No. IRT14R23), the Ministry of Education and the State Administration of Foreign Experts Affairs for the 111 Project (No. B13025), and the Innovation Program of Shanghai Municipal Education Commission. M.G.H. thanks the Australian Research Council for support (DP170100411). C.W. thanks the National and Shanghai Postdoctoral Program for Innovative Talents (nos. BX201800216 and 2018192)

A Congruent‐Melting Mid‐Infrared Nonlinear Optical Vanadate Exhibiting Strong Second‐Harmonic Generation

Study of mid-infrared (mid-IR) nonlinear optical (NLO) materials is hindered by the competing requirements of optimized second-harmonic generation (SHG) coefficient dij and laser-induced damage threshold (LIDT) as well as the harsh synthetic conditions. Herein, we report facile hydrothermal synthesis of a polar NLO vanadate Cs4V8O22 (CVO) featuring a quasi-rigid honeycomb-layered structure with [VO4] and [VO5] polyhedra aligned parallel. CVO possesses a wide IR-transparent window, high LIDT, and congruent-melting behavior. It has very strong phase-matchable SHG intensities in metal vanadate family (12.0 × KDP @ 1064 nm and 2.2 × AGS @ 2100 nm). First-principles calculations suggest that the exceptional SHG responses of CVO largely originate from virtual electronic transitions within [V4O11]∞ layer; the excellent optical transmittance of CVO arises from the special characteristics of vibrational phonons resulting from the layered structure.This research was financially supported by the National Natural Science Foundation of China (Nos. 51432006 and 52002276), the Ministry of Education of China for the Changjiang Innovation Research Team (No. IRT14R23), the Ministry of Education and the State Administration of Foreign Experts Affairs for the 111 Project (No. B13025), and the Innovation Program of Shanghai Municipal Education Commission. M.G.H. thank the Australian Research Council for support (DP170100411). Author thanks G.Z. and B.X.L. at FJIRSM for the LIDT measurements

Langasite Family Midinfrared Nonlinear Optical Oxide Materials: Structure, Property, and Applications

Midinfrared (IR) nonlinear optical (NLO) materials with high performance are vital in important technological applications in many civil and military fields. Very recently, langasite family compounds have attracted much attention due to their wide transparency to mid-IR region and ultrahigh laser damage threshold (LDT). In this brief review, three important compounds—LGS, LGN, and LGT—are investigated and analyzed based on available experimental data. The electrooptical (EO) Q-switch and mid-IR OPO applications are summarized in detail. Finally, promising search directions for new metal oxides that have good mid-IR NLO performances are discussed

Giant Optical Anisotropy in the UV-Transparent 2D Nonlinear Optical Material Sc(IO3 )2 (NO3 )

Birefringence is a fundamental optical property for linear and nonlinear optical (NLO) materials. Thus far, it has proved to be very difficult to engineer large birefringence in optical crystals functioning in the UV region. Herein, we report the first 2D rare-earth iodate-nitrate crystal Sc(IO3)2 (NO3) (SINO), which is shown to exhibit giant optical anisotropy. Air-stable SINO possesses a short UV absorption edge (298 nm), a strong NLO response (4.0 times that of benchmark KH2 PO4) for the nitrate family, and the largest birefringence (Δn=0.348 at 546 nm) of inorganic oxide optical crystals. The unusually large birefringence and NLO response can be attributed to an optimized 2D layered structure, combined with highly polarizable and anisotropic building units [IO3]- and [NO3]-. These findings will facilitate the development of UV linear and NLO materials with giant optical anisotropy and promote their potential application in optoelectronic devices.This research was financially supported by the National Natural Science Foundation of China (no. 51432006), the Ministry of Education of China for the Changjiang Innovation Research Team (no. IRT14R23), the Ministry of Education and the State Administration of Foreign Experts Affairs for the 111 Project (no. B13025), and the Innovation Program of Shanghai Municipal Education Commission. C.W. thanks the National and Shanghai Postdoctoral Program for Innovative Talents (nos. BX201800216 and 2018192). M.G.H. thanks the Australian Research Council for support (DP170100411)