When Octahedra Learn to Be Prisms: Unlocking a Record Deep‑UV NLO Crystal

2026-07-11

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Qi Gao

Hongping Wu *

Zhanggui Hu

Jiyang Wang

Yicheng Wu

Hongwei Yu *

DOI：10.1002/anie.1215467

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Deep ultraviolet (DUV) lasers are indispensable for cutting-edge science and technology, yet their practical realization is severely hampered by the performance trade-offs and growth limitations of existing nonlinear optical (NLO) crystals, such as the toxic and strongly layered KBe2BO3F2 (KBBF). Here, we challenge the conventional octahedral coordination preference and propose a paradigm for optimizing the arrangement of π-conjugated [B3O6] rings by steering cation-centered polyhedra toward triangular prismatic geometry. Guided by this design, we synthesize Na2CsCa2(B3O6)2F (NCCBF), a new DUV NLO crystal that integrates a large second harmonic generation response (5.5 × KH2PO4 (KDP)), a short ultraviolet (UV) cut-off edge (180 nm), a suitable birefringence (0.090 @ 532 nm), and low refractive index dispersion. Remarkably, centimeter-sized single crystals are grown via the top-seeded-solution-growth technique, and the material achieves the shortest phase-matchable wavelength among all known [B3O6]-based crystals. This work not only provides a promising candidate for high-power DUV laser output but also establishes a new structural design principle, promoting octahedral distortion toward trigonal prismatic geometry for unlocking the full potential of π-conjugated borate NLO crystals.

Keywords:

borate

deep-ultraviolet nonlinear optical crystal

octahedra collaborative strategy

π-conjugated [B3O6] group

When Octahedra Learn to Be Prisms: Unlocking a Record Deep‑UV NLO Crystal

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