Review of Heteroleptic Tetrahedra as Birefringent or Nonlinear Optical Motifs

Abstract

Birefringence and second harmonic generation are important to realizing the phase-matching capability and laser frequency conversion efficiency in a nonlinear optical (NLO) crystal. Heteroleptic tetrahedra have usually been used to design and explore birefringent or NLO materials, such as fluorooxo-heteroleptic tetrahedra BO x F 4−x (x = 1, 2, 3), PO x F 4−x (x = 2, 3), SO 3 F and other groups SiO 4−x N x (x = 1, 2, 3), PO 4−x S x (x = 1, 2, 3). Generally, heteroleptic tetrahedra exhibit larger microscopic properties than those of normal oxy-tetrahedra MO 4 (M = B, P, S, Si, etc.), which will improve the birefringence or NLO coefficients in a crystal. In this review, we systematically investigated the microscopic properties of heteroleptic tetrahedra which cover the deep-ultraviolet to the mid-infrared region, including SiO 4−x Nx (x = 2, 3), and BO 3 N. The structure-performance relationships of the related compounds with the above-mentioned heteroleptic tetrahedra were discussed through first-principles calculations. According to the computational results, some compounds with heteroleptic tetrahedra have good optical performances and can be used as potential ultraviolet or mid-infrared optical functional materials. This work will provide helpful insights into rational design and synthesis of new optical functional materials containing heteroleptic tetrahedra.

Second-harmonic-generation of [(Se,Te)Cl3]+[GaCl4]− with aligned ionic tetrahedra

“…In principle, they also stand for a large group of similar ionic compounds [ MX 3 ] + [ M ′ X 4 ] − ( M , M ′: metal or main-group element, X : halogen) with aligned tetrahedral building units, which are predominately known for silicates or phosphates until now. 6 In difference to many NLO materials, the strong effect is observed in the visible spectral range. Beside the experimental evaluation via the Kurtz-Perry approach, the SHG tensors are also determined based on density functional theory (DFT) calculation.…”

Tetrahedron-based deep-ultraviolet nonlinear optical crystal with optimized KBe2BO3F2-like structure and disordered cations

“…15 Second, tetrahedral units can also induce a large band gap and a strong SHG response when they are aligned with a large distortion. 24,25 Recently, tetrahedral units and tetrahedron-based DUV NLO crystals have attracted much attention, 26–29 for example, LiCs 2 PO 4 30 with a large band gap of 7.02 eV and a strong SHG response of 2.6 × KDP. With the increasing number of tetrahedron-based NLO crystals, relevant perspectives have been put forward to explain their strong SHG response, 31–33 while there are not enough examples to verify their universality.…”

“…15 Second, tetrahedral units can also induce a large band gap and a strong SHG response when they are aligned with a large distortion. 24,25 Recently, tetrahedral units and tetrahedron-based DUV NLO crystals have attracted much attention, [26][27][28][29] The LARS crystal possesses an optimized KBBFlike structure without any layered habit, which can be easily obtained by the aqueous solution method. In particular, it exhibits a large band gap and a strong SHG response, which are typically desired for tetrahedron-based DUV NLO crystals.…”

Modulating optical performance by phase transition in a nonlinear optical material β-Li2RbBi(PO4)2

“…1–5 Over the past decades, great efforts have been devoted to exploring UV/deep-UV NLO materials with excellent performance. 6–10…”

“…[1][2][3][4][5] Over the past decades, great efforts have been devoted to exploring UV/deep-UV NLO materials with excellent performance. [6][7][8][9][10] Currently, potential NLO materials are mostly limited to π-conjugated systems, especially for borates, carbonates, and nitrates. Consequently, a number of second harmonic generation (SHG) materials were discovered.…”