Kumbhakar Partha, Biswas Subrata, Kumbhakar Pathik
Nanoscience Laboratory, Department of Physics, National Institute of Technology Durgapur 713209 India
RSC Adv. 2019 Nov 19;9(65):37705-37713. doi: 10.1039/c9ra08166f.
Thanks to the advent of the random laser, new light applications have opened up, ranging from biophotonic to security devices. Here, by using the well-known but unexplored light-harvesting bio-pigment of butterfly pea (, CT) flower extract, generation of continuous-wave (CW) random lasing at ∼660 nm has been demonstrated. Furthermore, a wavelength tunability of ∼30 nm in the lasing emission was obtained by utilizing the resonance energy transfer (RET) mechanism in a gain medium with a binary mixture of CT extract and a commercially available methylene blue (MB) dye as the gain medium. In the CT extract-dye mixture, the bio-pigments are acting as donors and the MB dye molecules are acting as acceptors. Amplification in intensity of the lasing emission of this binary system has further been achieved in the presence of optimized concentrations of metal (Ag)-semiconductor (ZnO) scattering nanoparticles. Interestingly, the lasing threshold has been reduced from 128 to 25 W cm, with a narrowed emission peak just after loading of the Ag nanoplasmon in the ZnO-doped binary gain medium. Thanks to the strong localized electric field in the metal nanoplasmon, and the multiple scattering effects of ZnO, the lasing threshold was reduced by approximately four times compared to that of the gain medium without the use of scatterers. Thus, we believe that our findings on wavelength-tunable, non-toxic, biocompatible random lasing will open up new applications, including the design of low-cost biophotonic devices.
得益于随机激光的出现，新的光应用得以开拓，涵盖从生物光子学设备到安全设备等领域。在此，通过使用熟知但未被深入研究的蝶豆花提取物的光捕获生物色素（CT），已证明在约660 nm处产生连续波（CW）随机激光。此外，通过在增益介质中利用共振能量转移（RET）机制，以CT提取物和市售亚甲基蓝（MB）染料的二元混合物作为增益介质，在激光发射中获得了约30 nm的波长可调性。在CT提取物 - 染料混合物中，生物色素充当供体，MB染料分子充当受体。在优化浓度的金属（Ag） - 半导体（ZnO）散射纳米颗粒存在下，该二元系统的激光发射强度进一步得到增强。有趣的是，在ZnO掺杂的二元增益介质中加载Ag纳米等离子体后，激光阈值从128降低到25 W/cm，发射峰变窄。由于金属纳米等离子体中的强局域电场以及ZnO的多重散射效应，与不使用散射体的增益介质相比，激光阈值降低了约四倍。因此，我们相信我们关于波长可调、无毒、生物相容性随机激光的研究结果将开拓新的应用，包括低成本生物光子学设备的设计。
