Jiménez-Villar Ernesto, da Silva Iran F, Mestre Valdeci, Wetter Niklaus U, Lopez Cefe, de Oliveira Paulo C, Faustino Wagner M, de Sá Gilberto F
Departamento de Química Fundamental, Universidade Federal de Pernambuco, Cidade Universitária, 50670-901 Recife, PE, Brazil.
Departamento de Química and Departamento de Física, Universidade Federal da Paraíba, Cidade Universitária, 58051-970 João Pessoa, PB, Brazil.
ACS Omega. 2017 Jun 1;2(6):2415-2421. doi: 10.1021/acsomega.7b00086. eCollection 2017 Jun 30.
Anderson localization of light and random lasing in this critical regime is an open research frontier, which besides being a basic research topic could also lead to important applications. This article investigates the random laser action at the localization transition in a strongly disordered scattering medium composed of a colloidal suspension of core-shell nanoparticles (TiO@Silica) in ethanol solution of Rhodamine 6G. The classical superfluorescence band of the random laser was measured separately by collecting the emission at the back of the samples, showing a linear dependence with pumping fluence without gain depletion. However, frontal collection showed saturation of the absorption and emission. Narrow peaks of approximately equal intensity are observed on top of the classical superfluorescence band, indicating suppression of the interaction between the peaks modes. The linewidth of these peaks is lower than that of the passive modes of the scattering medium. A method called fraction of absorbed pumping allowed us to infer that this peak's mode (localized modes) is confined to a shallow region near the input-pumping border.
在这种临界状态下，光的安德森局域化和随机激光是一个开放的研究前沿领域，它不仅是一个基础研究课题，还可能带来重要应用。本文研究了在由罗丹明6G乙醇溶液中的核壳纳米颗粒（TiO@二氧化硅）胶体悬浮液组成的强无序散射介质中，处于局域化转变时的随机激光行为。通过收集样品背面的发射光，分别测量了随机激光的经典超荧光带，结果表明其与泵浦通量呈线性关系且无增益损耗。然而，正面收集显示吸收和发射出现饱和。在经典超荧光带之上观察到强度近似相等的窄峰，这表明峰模式之间的相互作用受到抑制。这些峰的线宽低于散射介质无源模式的线宽。一种称为吸收泵浦分数的方法使我们能够推断，这种峰模式（局域模式）局限于输入泵浦边界附近的浅区域。
