High‐Performance Sulfate Optical Materials Exhibiting Giant Second Harmonic Generation and Large Birefringence

Abstract

Discovering novel sulfate optical materials with strong second-harmonic generation (SHG) and large birefringence is confronted by a great challenge attributed to the intrinsically weak polarizability and optical anisotropy of tetrahedral SO 4 groups. Herein, two superior-performing sulfate optical materials, namely, noncentrosymmetric Hg 3 O 2 SO 4 and centrosymmetric CsHgClSO 4 • H 2 O, have been successfully synthesized through the introduction of a highly polarizable d 10 metal cation, Hg 2 + . The unique component layers in the reported compounds, [Hg 3 O 2 SO 4 ] ∞ layers in Hg 3 O 2 SO 4 and [HgClSO 4 (H 2 O)] À ∞ layers in CsHgClSO 4 • H 2 O, induce enlarged birefringence in each sulfate. Remarkably, Hg 3 O 2 SO 4 exhibits a very large SHG response (14 times that of KH 2 PO 4 ), which is the strongest efficiency among all the reported nonlinear optical sulfates. Detailed theoretical calculations confirm that the employment of highly polarizable Hg 2 + is an effective strategy to design superior optical materials with large birefringence and strong SHG response.

Mg(H2O)6[(IO2(OH))2(IO3)]2: a new iodate with a very large band gap and optical anisotropy

“…with second-order Jahn-Teller effect have been recommended. 23,37,38 The higher density and the optimal arrangement of the building blocks through suitable interactions such as hydrogen bonds in the structures also could boost the optical anisotropy of the target compounds. Guided by the above-mentioned strategy, a variety of promising NLO and birefringent crystals have been designed thus far.…”

Halogen regulation triggers structural transformation from centrosymmetric to noncentrosymmetric switches in tin phosphate halides Sn2PO4X (X = F, Cl)

“…Ultraviolet (UV) nonlinear optical (NLO) crystals with the capability of generating coherent light through a frequency doubling process in the UV wavelength are widely used in diverse technological and scientific fields, such as optical storage, semiconductor inspection, and telecommunications. [1][2][3][4][5][6][7][8][9][10] Generally, a UV NLO crystal with commercial potential should have several indispensable properties, that is, a large second harmonic generation (SHG) response, a wide transparency spectral range, moderate birefringence, and good physicochemical stability. [11][12][13][14][15][16][17] However, although a large number of UV NLO crystals were reported, crystals that have the abovementioned properties are scarce.…”

AAg2PS4(A = K, Na/K): the first-type of noncentrosymmetric alkali metal Ag-based thiophosphates exhibiting excellent second-order nonlinear optical performances

“…[1][2][3][4][5] Nowadays, NLO materials for ultraviolet (UV) and visible and near-infrared (NIR) wavelengths can basically satisfy the market's requirements and a great number of such materials with outstanding performances have been developed. [6][7][8][9][10][11][12][13] However, the development of NLO materials in the mid-IR (MIR) region is relatively insufficient. For example, commercially available ones like AgGaS 2 (AGS), 14 AgGaSe 2 (AGSe), 15 and ZnGeP 2 (ZGP) 16 possess large second-unique advantages as described below: (1) P possesses multiple oxidation states and the most common valences are +4 and +5, 29 and the P atom can exhibit diverse P-S anionic groups, such as [PS 4 ] 3− , [P 2 S 6 ] 4− , [P 2 S 7 ] 4− , [P 3 S 10 ] 5− , and [P 4 S 13 ] 6− , 30 which can further connect with other NLO-active motifs to establish polyanionic frameworks, covering zerodimensional (0D) clusters to three-dimensional (3D) networks.…”