Triphenylphosphine oxide (Triphenylphosphine oxide), with the chemical formula C18H15OP, is chemically alkaline, can interact with metal atoms, and can undergo redox reactions. The rigidity of its skeleton and the alkalinity of its oxygen atoms enable it to induce the crystallization of compounds that are difficult to crystallize by other methods. Triphenylphosphine oxide has a variety of applications in industry and scientific research, such as organic synthesis and pharmaceutical intermediates, catalysts, and extractants.
Miniaturized lasers are new light sources that can produce strong coherent light at the micro-nano scale. Continuous wave operation can promote the application of miniaturized lasers, but it is extremely challenging. The stimulated Raman scattering process provides a new way to generate continuous wave lasers. Due to the low Raman gain coefficient of inorganic materials, their Raman lasers rely on complex optical microcavity structures to enhance the interaction between light and matter. Organic materials have higher Raman gain coefficients, and high-quality microcavity structures can be obtained through a simple self-assembly process, which is expected to achieve efficient continuous wave Raman lasers.
Although there is still a blank in the research of organic materials in continuous wave Raman laser, the designability of organic molecules provides an opportunity to enhance the Raman gain coefficient and thus realize continuous wave Raman laser. Some work has developed a strategy for synthesizing organic dimers by metal-organic coordination, which induces the oligomerization effect and rigidity effect of organic functional groups, and can superlinearly improve the Raman gain coefficient of the vibration mode of organic molecules near the metal connector, providing the possibility of realizing organic continuous wave Raman laser.
The researchers selected triphenylphosphine oxide (TPPO) with Raman activity and lone pair electron coordination sites as a model organic compound, and divalent metal halide zinc chloride (ZnCl2) as a metal connector, and synthesized organic dimers (ZnCl2(TPPO)2) through metal-organic coordination reaction. The researchers developed a method for molecular self-assembly of thermal saturated solution to prepare high-quality organic monomer and dimer microcrystals.
Compared with organic monomer microcrystals, metal-bonded organic dimer microcrystals exhibit significantly enhanced spontaneous Raman scattering, corresponding to a greatly improved Raman gain coefficient. Accordingly, unlike organic monomer microcrystals, metal-bonded organic dimer microcrystals support low-threshold continuous wave Raman lasing. Moreover, compared with organic monomer microcrystals, metal-bonded organic dimer microcrystals have higher stability, which can ensure the long-term stable operation of continuous wave Raman lasers.
As a third-order nonlinear effect, stimulated Raman scattering itself supports laser wavelength tuning (. Moreover, organic dimer microcrystals have a large optical band gap and show a very wide transparent window (360~1580 nm). Therefore, by simply adjusting the wavelength of the excitation light, laser emission of multiple wavelengths in the visible-near infrared range (422, 465, 562, 678, 852, 1190 nm).
In general, this work developed a strategy for synthesizing organic dimers through metal-organic coordination, which induced the oligomerization effect and rigidity effect of organic functional groups, and can superlinearly improve the Raman gain coefficient of the vibration mode of organic molecules near the metal linker, making it possible to realize organic continuous wave Raman laser. The researchers selected triphenylphosphine oxide (TPPO) with Raman activity and lone pair electron coordination sites as a model organic compound, and divalent metal halide zinc chloride (ZnCl2) as a metal linker, and synthesized an organic dimer (ZnCl2(TPPO)2) through metal-organic coordination reaction. They also developed a method for molecular self-assembly in thermal saturated solution, high-quality organic monomer and dimer microcrystals were prepared. Compared with organic monomer microcrystals, metal-bonded organic dimer microcrystals exhibit significantly enhanced spontaneous Raman scattering, corresponding to a greatly improved Raman gain coefficient. Accordingly, unlike organic monomer microcrystals, metal-bonded organic dimer microcrystals support low-threshold continuous-wave Raman lasing. Moreover, compared with organic monomer microcrystals, metal-bonded organic dimer microcrystals have higher stability, which can ensure the long-term stable operation of continuous-wave Raman lasers. Stimulated Raman scattering, as a third-order nonlinear effect, itself supports laser wavelength tuning. In addition, organic dimer microcrystals have a large optical band gap and exhibit a very wide transparency window (360~1580 nm).
