Shedding Light on the Structure and Characterization of K₂ZnGe₂O₆: A Phase-Matchable Nonlinear Optical Crystal

Abstract

Nonlinear optical (NLO) materials have recently aroused great interest owing to their capability of frequency conversion in solid-state lasers. Herein, we report an acentric zinc germanate K2ZnGe2O6 obtained successfully through spontaneous crystallization methods. It affords a novel three-dimensional (3D) framework comprised of [GeO4] and [ZnO4] motifs with K atoms located in the tunnels. K2ZnGe2O6 displays a moderate second-harmonic-generation (SHG) intensity (0.73 × KDP) with phase-matchable behavior. Optical characterization demonstrated that it has a UV cutoff edge located at 368 nm with a large energy band of 3.23 eV, accompanied by a wide transmission window, covering a 3–5 μm atmospheric window. Moreover, thermal properties implied that it possesses intriguing thermal stability of 987 °C and a congruent melting nature. Additionally, first-principles calculations unveiled that the NLO performance was primarily attributed to the collective effect of [GeO4] and [ZnO4] building units. These findings indicate that K2ZnGe2O6 is a potential NLO crystal.

An effective pathway to design and synthesize UV birefringent crystalsviarational assembly of π-conjugated [CO3]2−and [NO3]−triangles

“…Metal-centered polyhedra also have impacts on the structure and optical properties of crystals. Similar to stereochemically active lone pair (SCALP) cations or d 0 metal cations, they can positively affect the birefringence, 45,46 such as the SCALP Sn 2+ atom in Sn 2 PO 4 I (0.664 at 532nm), 47 the [WO 5 F] 5À octahedron in KWO 3 F (0.088 at 1064nm), 48 etc. However, these metal cations play a negative role in the transmission of UV light.…”

Two Chiral YbIII Enantiomeric Pairs with Distinct Enantiomerically Pure N-Donor Ligands Presenting Significant Differences in Photoluminescence, Circularly Polarized Luminescence, and Second-Harmonic Generation

“…The SHG intensity of Yb- R -1 is also much larger than a multifunctional Zn II –Yb III enantiomer (0.2 × KDP), a 2D Ag­(I) enantiomer (0.36 × KDP), and a pair of chiral Cu­(I) coordination polymers (0.36 × KDP) and is slightly larger than an eight-coordinated Dy III enantiomeric pair (0.7 × KDP) . It is even larger than some SHG-active inorganic materials, such as K 2 [Te 3 O 8 (OH) 4 ] (0.6 × KDP), CsKB 8 O 12 F 2 ·CsI (0.6 × KDP), and K 2 ZnGe 2 O 6 (0.73 × KDP) . According to eq and χ R (2) = 0.39 pm V –1 for KDP, the second-order NLO susceptibilities ( χ S (2) ) of Yb- R -1 and Yb- R -2 are calculated to be 0.35 and 0.12 pm V –1 , respectively. The precursor Yb­(tta) 3 (H 2 O) 2 only presents a strong THG response at λ = 517 nm (Figure S12) because it crystallizes in a centrosymmetric P 1̅ space group of the triclinic system .…”

“…48 It is even larger than some SHG-active inorganic materials, such as K 2 [Te 3 O 8 (OH) 4 ] (0.6 × KDP), 87 CsKB 8 O 12 F 2 •CsI (0.6 × KDP), 88 and K 2 ZnGe 2 O 6 (0.73 × KDP). 89 According to eq 1 and χ R…”

LiVTeO5: a mid-infrared nonlinear optical vanadium tellurate crystal exhibiting enhanced second harmonic generation activities and notable birefringence

“…Nonlinear optical (NLO) materials capable of generating coherent and tunable lasers through frequency conversion capability, particularly those with the mid-infrared (IR) region covering the crucial atmospheric window (3-5 μm), have garnered significant interest in science and technology. [1][2][3][4][5] In recent years, significant strides have been made in the realm of design, synthesis, property characterization, and structureproperty elucidation of mid-IR NLO compounds. Prominent examples include commercially available chalcogenide-and pnictide-based crystals, AgGaQ 2 (Q = Se, S) and ZnGeP 2 .…”