Improving the Random Lasing Performance using Au@SiO2 Nanocubes-Silver Film Hybrid Structure

Abstract Metal films are extensively used as electrodes in optoelectronic devices. However, quenching caused by metal film is harmful to lasing and a main barrier to developing electrically pumped lasers. In this study, a dramatic threshold reduction is reported for random lasing based on a plasmonic hybrid structure of (Au core)-(SiO2 shell) nanocubes deposited on Ag film (Au@SiO2 NCs-Ag film). This hybrid structure could more significantly lower the lasing threshold than Ag film or Au@SiO2 NCs. In particular, the SiO2 shell simultaneously tuned the interactions of localized surface plasmons (LSPs) of the Au NC cores with surface plasmon polariton (SPP) of the Ag film and gain medium. The optimal thickness of the SiO2 shell was determined that could result in the lowest lasing threshold: 14.1% that of the neat gain medium. Furthermore, compared to a hybrid structure consisting of Ag film with regular metal nanoparticles, Au@SiO2 nanospheres, the gain medium based on a hybrid Au@SiO2 NCs-Ag film structure had a lower lasing threshold. This was attributed to the stronger electric field enhancement and scattering of the Au NC cores than the Au nanosphere cores, ensuring marked plasmonic interaction between the SPP of the Ag film and the LSPs of the Au NC cores. Our results provide a convenient method to lower the lasing threshold of the gain medium in the presence of metal film.