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Updated: Jun 7, 2025

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications
Published on: June 2, 2017
Large second harmonic generation and birefringence from extended octupolar π-conjugated structures
Danyang Dou1, Bingbing Zhang1,2, Daqing Yang1
1College of Chemistry and Materials Science, Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of the Ministry of Education, Hebei Research Center of the Basic Discipline of Synthetic Chemistry, Key Laboratory of Chemical Biology of Hebei Province, Hebei University Baoding 071002 China wangy@hbu.edu.cn.
Abstract:
The exploration of crystal materials for optical manipulation by nonlinear optical (NLO) and anisotropic light-matter interaction is of paramount importance in modern science and technology. However, in such crystal materials, finding the right balance between second harmonic generation (SHG), birefringence, and the bandgap presents a significant challenge. In this contribution, we employ extended octupolar π-conjugated groups devoid of intrinsic dipole moments to construct melonate-based inorganic-organic hybrid crystals, thereby achieving simultaneous large optical nonlinearity and anisotropy. In accordance with this strategy, Rb3[C6N7(NCN)3]·3H2O (I) and Cs3[C6N7(NCN)3]·3H2O (II) were obtained and subjected to detailed investigation. Strong SHG responses of ∼9× KH2PO4 and a large birefringence of at least 0.6@546 nm were observed for I and II crystals, respectively, together with a suitable bandgap for visible-UV application. Theoretical calculations indicated that octupolar [C6N7(NCN)3]3- groups of I and II arranged in a near parallel configuration exhibit a discrete π electron distribution, resulting in enhanced NLO susceptibilities and maximal polarizability difference. This work underscores the potential of octupolar structures with extended π-conjugation as a promising avenue for the discovery of NLO and birefringence crystals.
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