Hongbo Huang, Yinsong Zhao, Yining Wang, Jiaxing Wang, Hanyu Chen, Daqing Yang, Ying Wang*, Bingbing Zhang*

Cite this article: https://doi.org/10.1016/j.cjsc.2026.101102

Publication date:

Keywords: Ultraviolet nonlinear optical crystals; Charge and structural flexibility; Second-harmonic generation; 266 nm laser output; Birefringence

ABSTRACT

The development of high-performance ultraviolet (UV) nonlinear optical (NLO) crystals is expected to drive advances in laser science and technology. Materials that simultaneously exhibit broad UV transparency, large birefringence, and a strong second-harmonic generation (SHG) response remain critically scarce. In this work, the [C4H4O6]2- unit, composed of π-conjugated and non-π-conjugated motifs, is introduced to design UV NLO crystals by leveraging its charge and structural flexibility. Six tartrate crystals, including both known structures and new phases, have been systematically evaluated for their linear and nonlinear optical properties. Among them, Ca[L-C4H4O6] and Sr[L-C4H4O6] stand out particularly, demonstrating short UV cut-off edges (206 and 203 nm), large birefringence (0.19 and 0.17@546 nm), and strong SHG capabilities (3.5 and 3.0 × KDP, 0.37 and 0.43 × BBO). Notably, the shortest phase-matching wavelength reach 219 nm and 226 nm, respectively, which cover the key working wavelength of 266 nm generated as the fourth harmonic of a fundamental 1064 nm laser. Ca[L-C4H4O6] also exhibits relatively good thermal and chemical stability, with the laser-induced damage threshold as high as 1.01 GW/cm2. The outstanding performance and sufficient stability of the materials enable a breakthrough in organic-inorganic hybrid UV NLO crystals.