麻豆淫院

In the field of nonlinear optics (NLO), deep-ultraviolet (DUV) NLO crystals have garnered attention due to their crucial role in all-solid-state lasers. With ongoing research, the demand for these DUV NLO crystals continues to grow.

Currently, DUV NLO crystals that simultaneously exhibit a large optical band gap and strong second harmonic generation (SHG) response are mainly found in carbonates, borates, and nitrates containing 蟺-conjugated elements. In contrast, sulfates and phosphates, without 蟺-conjugated functions, typically struggle to achieve similar performance due to their smaller microscopic second-order polarizability.

Most DUV NLO phosphates having SHG responses struggle to exceed the performance limit of 3 脳 KDP. A research group led by Prof. Zhu Qilong and Prof. Lin Hua from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences proposed a "polar-axial-symmetry screening" strategy to overcome this challenge.

The study was in Angewandte Chemie International Edition.

Researchers discovered a magnesium-based phosphate compound, Mg₂PO₄Cl, among more than 10,000 phosphates. This compound exhibited the highest SHG response (5.2 脳 KDP) among DUV NLO crystals containing non-蟺-conjugated elements, with a cutoff edge estimated at 179 nm and a birefringence of 0.046@1064 nm according to hybrid functional calculations.

First-principles calculations indicated that the excellent NLO performance of Mg₂PO₄Cl primarily arose from the effective stacking of three functional motifs, [PO₄], [MgO₅Cl], and [MgO₄Cl₂], along the polar axis [001], where non-bonding electrons of O-2p and Cl-3p were preferentially aligned in the same direction.

Berry phase analysis revealed the role of the hybridization degree of P鈥揙 bonds in enhancing the SHG response. Moreover, a detailed analysis of the structure-property relationships of other advanced DUV NLO compounds containing non-蟺-conjugated elements further validated the effectiveness of this polar-axial-symmetry screening strategy.

The findings of this study not only demonstrated the immense potential of phosphate compounds in the DUV NLO crystal field, but also provided insights for future crystal design. The polar-axial-symmetry screening strategy will help deepen the understanding of structure-property relationships and promote the development of NLO crystal materials.