Metal-Dielectric Core-Shell Nanoparticles: Advanced Plasmonic Architectures Towards Multiple Control of Random Lasers

Random lasing properties of dye solutions suspended with gold-silica core-shell nanoparticles are investigated. The core-shell architecture allows adjustment of plasmon coupling strength between metal and optical gain media by varying the thickness of dielectric shell. Consequently, multiple aspects of random lasers can be controlled, such as mode interactions, lasing spikiness, and pump threshold. The results show that bare gold nanoparticles give rise to the most profound lasing spikes that are evenly separated in resonant wavelength. The lowest threshold is observed when the shell thickness is similar to 14.6 nm. The experimental observations are interpreted in terms of resonant coupling between metal nanoparticles and fluorophores, localization of pump light and lasing modes at the surface of metal, as well as plasmonic modifications of absorption and pump rates of fluorophores. The results suggest that metal-dielectric core-shell nanostructures can serve as promising candidates towards development of well-controlled random lasers.