Progress in the Research of Continuous Wave Laser in Chemical Industry

Laser plays an important role in fields such as photonic chips, laser displays, and in vehicle radars. Organic materials have advantages such as molecular diversity, energy level richness, heterogeneous compatibility, and ease of processing. They have significant advantages in the construction of high-performance and multifunctional lasers and are expected to further innovate laser technology and applications.

At present, organic lasers rely on large-sized pulse pumping sources, which is not conducive to the integration of functional devices and limits the application range of organic lasers. Therefore, the development of organic continuous wave lasers has important scientific significance and application value, and organic continuous wave laser materials are the key in this field. 

In recent years, Zhao Yongsheng, the research group of the Key Laboratory of the School of Optics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, has been committed to the research of organic laser materials, and has carried out systematic research work in the design of low threshold laser materials, high-quality microcavity synthesis, quasi continuous wave laser device construction, etc. Recently, the Zhao Yongsheng and Dong Haiyun research groups at the Institute of Chemistry have developed a strategy for improving the Raman gain of organic molecules by metal bonded organic dimers. Based on stimulated Raman scattering of organic microcrystals, continuous wave laser emission has been achieved. 

At present, there is little research on the use of organic materials in continuous wave Raman lasers. The designability of organic molecules provides an opportunity to enhance Raman gain coefficient and achieve continuous wave Raman lasers. This study developed a strategy for synthesizing organic dimers through metal organic coordination, inducing oligomerization and rigidity effects of organic functional groups, which can superlinearly increase the Raman gain coefficient of organic molecules in the vibration mode near metal connectors, providing the possibility for achieving organic continuous wave Raman lasers.

Researchers have selected triphenylphosphine oxide (TPPO) with Raman activity and lone pair electron coordination sites as the model organic compound, using divalent metal halide zinc chloride (ZnCl2) as the metal linker, to synthesize an organic dimer (ZnCl2 (TPPO) 2) through a metal organic coordination reaction. Researchers have developed a method of self-assembly of molecules in thermally saturated solutions to prepare high-quality organic monomers and dimer microcrystals.

Compared to organic monomer microcrystals, metal bonded organic dimer microcrystals exhibit significantly enhanced spontaneous Raman scattering, corresponding to a significantly increased Raman gain coefficient. Unlike organic monomer microcrystals, metal bonded organic dimer microcrystals support low threshold continuous wave Raman lasers.

Meanwhile, compared to organic monomer microcrystals, metal bonded organic dimer microcrystals have higher stability, ensuring long-term stable operation of continuous wave Raman lasers. Stimulated Raman scattering, as a third-order nonlinear effect, supports laser wavelength tuning. And organic dimer microcrystals have large optical bandgaps, exhibiting a very wide transparent window (360-1580nm).

Therefore, researchers have achieved multiple wavelengths of laser emission in the visible near-infrared range (422, 465, 562, 678, 852, 1190nm) in organic dimer microcrystals by regulating the excitation wavelength. The metal bonded organic dimer strategy can significantly improve the Raman gain coefficient of organic molecules and the stability of organic microcrystalline materials, providing a new platform for exploring organic continuous wave micro nano lasers. 

The relevant research results are published in the German Journal of Applied Chemistry. The research work was supported by the National Natural Science Foundation of China, the Ministry of Science and Technology and the Chinese Academy of Sciences.

Source: Institute of Chemistry