Yadav Renu, Pal Sourabh, Jana Subhajit, Roy Shuvajit, Debnath Kapil, Ray Samit K, Brundavanam Maruthi M, Bhaktha B N Shivakiran
Department of Physics, Indian Institute of Technology Kharagpur, Kharagpur-721302, India.
Advanced Technology Development Centre, Indian Institute of Technology Kharagpur, Kharagpur 721302, India.
Phys Chem Chem Phys. 2023 Oct 25;25(41):28336-28349. doi: 10.1039/d3cp04151d.
Metal nanoparticles (NPs) can be employed to modify the emission level of a dye emitter by tailoring the spectral overlap of the optical gain and localized surface plasmon resonance (LSPR). In the case of plasmonic random lasers, tuning the spectral overlap by manipulating metal NPs changes the scattering properties of the system, which is crucial in random lasers (RLs). In order to overcome this drawback, the emitter gain spectrum across the LSPR is tuned by appropriately choosing various dye emitters. A system with Au nanoislands (NIs) randomly distributed on the surface of vertically aligned ZnO nanorods on a glass substrate coated with three different dye emitters has been employed to study the metal-gain interaction as a function of spectral overlap. It is observed that the photoluminescence is quenched in the presence of Au NIs for all the three dye emitters; however, the degree of quenching is found to be directly proportional to the extent of spectral overlap of the LSPR and the fluorophore emission spectrum, with the resonantly coupled systems exhibiting higher random lasing thresholds. However, a dequenching of the emission is observed under spectrally off-resonant conditions, leading to a lower threshold RL. The effect of tailoring of the metal-gain interaction on the coherent and incoherent intensity components of RL emission is studied to elucidate the contrasting results of photoluminescence and RL emission. As the optical gain shifts away from the LSPR peak, the RL emission is dominated by the coherent intensity. The speckle-like field distributions of the RL modes couple to the plasmonic nanocavities along with a reduced absorption loss for the off-resonant case, leading to an enhanced stimulated emission. Hence, a synergy between random laser modes, plasmonic nanocavities and optimum spectral overlap has been utilized as a tool to dequench the plasmon quenched fluorophore emission.
金属纳米颗粒（NPs）可用于通过调整光学增益与局域表面等离子体共振（LSPR）的光谱重叠来改变染料发射体的发射水平。在等离子体随机激光器的情况下，通过操纵金属纳米颗粒来调整光谱重叠会改变系统的散射特性，这在随机激光器（RLs）中至关重要。为了克服这一缺点，通过适当选择各种染料发射体来调整跨越LSPR的发射体增益光谱。采用了一个系统，其中金纳米岛（NIs）随机分布在涂覆有三种不同染料发射体的玻璃基板上垂直排列的氧化锌纳米棒表面，以研究金属 - 增益相互作用作为光谱重叠的函数。观察到，对于所有三种染料发射体，在存在金纳米岛的情况下光致发光都会淬灭；然而，淬灭程度与LSPR和荧光团发射光谱的光谱重叠程度成正比，共振耦合系统表现出更高的随机激光阈值。然而，在光谱非共振条件下观察到发射的去淬灭，导致较低阈值的随机激光器。研究了金属 - 增益相互作用的调整对随机激光发射的相干和非相干强度分量的影响，以阐明光致发光和随机激光发射的对比结果。随着光学增益从LSPR峰值移开，随机激光发射由相干强度主导。随机激光模式的斑点状场分布与等离子体纳米腔耦合，同时非共振情况下的吸收损耗降低，导致受激发射增强。因此，随机激光模式、等离子体纳米腔和最佳光谱重叠之间的协同作用已被用作去淬灭等离子体淬灭的荧光团发射的工具。
