Research progress on ultra-wide bandgap infrared NLO crystal materials of Fujian Institute of Physics

[ Instrument R & D of Instrument Network ] Mid-infrared nonlinear optical (NLO) crystal materials have important applications in the laser field (such as lidar, laser communication, infrared telemetry, photoelectric countermeasures, etc.). At present, the main materials used in the infrared band are AgGaS2, AgGaSe2, and ZnGeP2. These materials have the advantages of large NLO coefficient and wide transmission range in the mid-to-far infrared band. However, they also have problems such as low laser damage threshold or two-photon absorption. To meet the requirements of the development of high-power lasers, the exploration of new crystal materials with large NLO coefficients and high laser damage thresholds has become the key to breakthroughs in this field.

The research team led by Guo Guocong, a researcher at the State Key Laboratory of Structural Chemistry of Fujian Institute of Material Structure, Chinese Academy of Sciences, with the support of the Chinese Academy of Sciences ’Strategic Leading Science and Technology Project and the National Natural Science Foundation of China, is difficult to achieve both the large NLO coefficient and the high laser damage threshold The bottleneck of the structural design of the structure, adopts the structural design idea of ​​double "functional primitives", that is, the "laser damage functional primitives" (polycationic groups are constructed from elements with large differences in electronegativity to increase the band gap and thus increase the laser damage threshold ) And "NLO active functional element" (introducing covalent structural units to increase the NLO coefficient) at the molecular level to assemble into a centerless structure, successfully synthesized the first nanopore framework constructed by a single tetrahedron The chalcogenide compound Li [Cs2LiCl] [Ga3S6]. The ordered stacking of GaS4 tetrahedral structural units in the compound obtains a large NLO coefficient (0.7 times AgGaS2), and the alkali metal halide guest interspersed in the nanopores makes the compound have the widest optical band in chalcogenide NLO materials Gap (4.18 eV), showing a high laser damage threshold (4.1 times AgGaS2). At the same time, the compound has a wide infrared transmission range and phase matching, and is an excellent infrared NLO candidate material. Relevant research work is titled Li [LiCs2Cl] [Ga3S6]: A Nanoporous Framework of GaS4 Tetrahedra with Excellent Nonlinear Optical Performance, as a positive cover article published in Angew. Chem. Int. Ed. 2020, 59, 4856–4859. DOI: 10.1002 / anie.201912416, associate researcher Liu Binwen is the first author of the paper, associate researcher Jiang Xiaoming and researcher Guo Guocong are corresponding authors.

Previously, the research team first proposed the academic idea of ​​"functional motif" in 2001 (Progress In Chemistry, 2001, 13, 151); designed a new infrared NLO functional motif (Chem. Mater. 2017, 29, 9200); broke through the bottleneck that the large NLO coefficient and high laser damage threshold are difficult to achieve (Chem. Sci. 2016, 7, 6273); obtained a variety of high-performance NLO new materials through various structural design strategies (J. Am. Chem. Soc. 2011, 133, 3410; Chem. Sci. 2018, 9, 5700; Adv. Optical. Mater. 2018, 1800156; Chem. Mater. 2017, 29, 1796; Chem. Mater. 2015, 27, 8189).