Hosseini Mandana Sadat, Yazdani Elnaz, Sajad Batool
Department of Physics, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran.
Department of Physics, Faculty of Physics and Chemistry, Alzahra University, Tehran, Iran.
Sci Rep. 2021 Nov 5;11(1):21747. doi: 10.1038/s41598-021-01354-8.
This study reports the first experimental observation of cascaded stimulated Raman scattering (SRS) generation in a colloidal disordered medium. Generation of the cascaded effect requires both a high Raman gain and pump power in the disordered medium. Here, to extend effective path lengths of photons into the Raman gain medium for producing additional SRS processes, ZnO microspheres with abundant nano-protrusions as suitable scattering centers are proposed. It is explained that nano-protrusions on the surface of the spheres can act as nano reflectors and significantly provide potent feedback in the disordered system. This provided feedback via nano-protrusions boosts cascaded SRS generation to allow the appearance of higher Raman signals of Rhodamine 6G dye solution at a low scatterer concentration of 5 mg/ml. The threshold for the formation of the first Raman signal is measured at about 60 mJ/pulse. Also, the evolution of Raman signals under several fixed pump pulses is examined to investigate the stability from pulse to pulse. Our findings provide promising perspectives for achieving the single-frequency laser sources and generate desirable wavelengths for specific applications.
本研究报告了在胶体无序介质中首次对级联受激拉曼散射（SRS）产生进行的实验观察。级联效应的产生需要无序介质中具有高拉曼增益和泵浦功率。在此，为了将光子的有效路径长度扩展到拉曼增益介质中以产生额外的SRS过程，提出了具有丰富纳米突起的ZnO微球作为合适的散射中心。据解释，球体表面的纳米突起可充当纳米反射器，并在无序系统中显著提供有效的反馈。这种通过纳米突起提供的反馈促进了级联SRS的产生，从而使得在5mg/ml的低散射体浓度下出现罗丹明6G染料溶液的更高拉曼信号。第一个拉曼信号形成的阈值测量为约60mJ/脉冲。此外，还研究了在几个固定泵浦脉冲下拉曼信号的演变，以研究脉冲之间的稳定性。我们的研究结果为实现单频激光源并为特定应用产生所需波长提供了有前景的前景。
