Phosphate deep ultraviolet nonlinear optical crystal material research progress in Xinjiang Institute of Physics and Chemistry

The nonlinear optical crystal is an important photoelectric information functional material, which has a wide range of application prospects in the fields of information, scientific research, energy, industrial manufacturing, and medical and health care. With the rapid development of laser precision machining industry, laser chemistry, ultraviolet laser spectroscopy and laser medicine, people urgently need to develop all-solid-state deep-UV coherent light sources. The key breakthrough lies in the deep-UV waveband (spectrum range below 200nm). The development and application of nonlinear optical crystals. In recent years, in the newly developed deep ultraviolet non-linear optical crystal materials, phosphate materials have become a recent research hotspot because of their advantages of short UV cut-off edge. However, the second order frequency multiplication coefficient of the PO4 functional group in phosphate is only one-tenth of that of the plane BO oxygen group (B3O6 and BO3), resulting in the phosphate material having a defect of a smaller frequency multiplier coefficient. Therefore, it is necessary to effectively increase the frequency-doubling effect by reasonably designing the combination and arrangement of the functional groups while ensuring the wide transmission range of the phosphate. The research team of Pan Shilie, a laboratory of new photoelectric functional materials of the Xinjiang Institute of Physics and Chemistry, Chinese Academy of Sciences, has been devoted to the research of new nonlinear optical crystals in recent years. Based on the research results of composite alkali metal borate nonlinear optical crystal materials in the early stage, through the introduction of alkali metal cations with large ionic radii in the phosphate, the research team successfully designed and synthesized a phosphate deep ultraviolet nonlinear optical crystal. Material LiCs2PO4. The compound exhibits not only a short UV cut-off edge (174 nm) but also a large frequency-doubling effect (2.6 times KDP), which is the compound with the highest frequency-doubling effect in the phosphate deep UV nonlinear optical crystal material system. At the same time, LiCs2PO4 can achieve phase matching at 1064 nm, and the crystal is easy to grow, which is expected to be a new type of deep ultraviolet nonlinear optical crystal material. In addition, the material is orthophosphate, and the mechanism of the source of the large frequency multiplier effect is different from the polyphosphoryl group double frequency gain effect proposed by other research groups. The researchers calculated the optical properties of the material through first principles, and found that the crystal structure of the material has a co-edge connection of LiO4-PO4 groups, and this special connection method is beneficial to O-2p non- The directional arrangement of the key tracks results in an effective superposition of the microscopic nonlinear optical coefficients of the phosphorus oxygen structural elements, so that LiCs2PO4 exhibits a relatively large frequency-doubling effect. This work provides new research ideas for the design of nonlinear optical crystal materials with large frequency-doubling effect in phosphates. Related research results were published on J. Am. Chem. Soc. Pan Shilie Research Team Master Li Lin and Assistant Researcher Wang Ying are the co-first authors of the paper. The research work was supported by the National Natural Science Foundation of China and the "Light of the West" of the Chinese Academy of Sciences. Orientational Arrangement of O-2p Non-bonded Orbitals in LiCs2PO4 Causes Larger Frequency-doubled Effect