New phenolic N-methylquinolinium single crystals for second-order nonlinear optics

•New highly efficient nonlinear optical hydroxystyryl N-methylquinolinium single crystals are developed.•Bulk quinolinium crystals with a size of up to 56 mm2 are successfully grown.•Large transparency range in optical region and relatively low absorption coefficient in THz region.

Highly efficient nonlinear optical quinolinium single crystals are newly designed and synthesized. The quinolinium single crystals consist of a 2-(4-hydroxystyryl)-1-methylquinolinium cation possessing large molecular optical nonlinearity and a 2,4,6-trimethylbenzenesulfonate counter anion. The quinolinium crystals exhibit monoclinic acentric space group P21 symmetry, resulting in large macroscopic nonlinear optical response, which is comparable with those of highly nonlinear optical configurationally locked polyene crystals. Plate-shaped bulk quinolinium crystals with an area of up to 56 mm2 are successfully grown by the solution growth method. Single quinolinium crystals exhibit a large transparency range (550–1600 nm) in the optical region and a relatively low absorption coefficient in the THz region.

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