Achieving Large Second Harmonic Generation Effects via Optimal Planar Alignment of Triangular Units

Abstract

Trigonal planar units with large polarizability anisotropy and high physicochemical stability are ideal structural units for exploring nonlinear optical (NLO) materials. Integrating the merits of two types of triangular-like moieties, a family of second-order NLO-active hybrid halides, MATX (X = Cl (1), Br (2), and I (3)), are achieved. MATX crystallizes in a nonpolar space group of P 62c but exhibits the optimal spatial arrangement and superior NLO performance. The low coordination planar trigonal AgX 3 units enable segregation in layers of the three-winged propeller-like Me 3 TPA units. All of the layers are packed in a perfect parallel fashion, making the functional materials exhibit superior NLO performances, including the phase matchable behavior with strong SHG responses (6.2/1, 6.5/2, and 7.6/3 times that of potassium dihydrogen phosphate), large birefringence (0.232/1, 0.252/2 and 0.260/3 at 1064 nm), high laser damage threshold, wide transparent window, and easiness of crystal growth. The first-principles calculations reveal that the coexistence of strong linear and nonlinear optical properties are ascribed to the synergistic effect of the trigonal moieties. This study points out a useful path for the rational design of excellent NLO materials.

Sb4O3(TeO3)2(HSO4)(OH): An Antimony Tellurite Sulfate Exhibiting Large Optical Anisotropy Activated by Lone Pair Stereoactivity

“…Birefringent crystalline materials have the ability to modulate and polarize light, which are very important in photoelectric functional areas, and have been widely used as polarized prisms, optical isolators, circulators, and Q-switches. − At present, typical birefringent crystals, such as CaCO 3 , YVO 4 , MgF 2 , α-BaB 2 O 4 (α-BBO), and LiNbO 3 , have been widely utilized in commercial applications. However, these materials still suffer from some drawbacks such as unbefitting birefringence or a limited transparent window.…”

KCs2[GaB5O10](OH): A Zeolitic Galloborate Framework with a Nonlinear Optical Property

“…In the past two decades, replacing SiO 4 with four-connected oxoboron clusters results in the rapid developments of aluminoborates (ABOs). − In contrast to tetrahedrally coordinated silicon in zeolite chemistry, boron atoms in the oxoboron clusters can be surrounded by three or four oxygen atoms, of which the BO 3 triangles with π-conjugated systems would greatly enhance the probability of acentric structures, which is the prerequisite of nonlinear optical (NLO) materials. − Meanwhile, the different linking modes between AlO 4 and four-connected oxoboron clusters can generate various 3D zeolitic frameworks with different topologies, − greatly enriching the structural diversity of borates. To further explore new members of zeolitic borates, large efforts have been paid on replacing AlO 4 with GaO 4 or GeO 4 , − considering that the larger cationic radius would bring forth novel zeolitic frameworks different from ABOs, but progress is still relatively slow.…”

[C(NH2)2NHNO2][C(NH2)3](NO3)2: A Mixed Organic Cationic Hybrid Nitrate with an Unprecedented Nonlinear-Optical-Active Unit

“…Organic–inorganic hybridization has been proven to be a useful method that could perfectly inherit the advantages of two kinds of structural units. − Taking the organic–inorganic hybrid compound (C 5 H 6 ON) + (H 2 PO 4 ) − (4HPP) as an example, the (C 5 H 6 ON) + cation has significant polarizability anisotropy (δ) and hyperpolarizability (β). Combining the π-conjugated (C 5 H 6 ON) + cation with the inorganic (H 2 PO 4 ) − anionic group fully promotes the formation of an ideal noncentrosymmetric (NCS) structure.…”