Coupling colloidal quantum dot supraparticle microlasers with surface plasmon resonances via plasmonic gold substrates

The miniaturisation of semiconductor lasers to the nanoscale is difficult because of increasing losses as the laser cavity size approaches the wavelength of light, with some recent efforts focusing on high-refractive index dielectric materials and plasmonics to try and overcome this challenge. With this in mind, we immobilize CdSe1-xSx/ZnS colloidal quantum dot (CQD) supraparticle (SuP) microlasers onto gold nanoparticle (AuNP) coated glass substrates. We study the interaction of the absorption, the non-resonant luminescence, and the whispering gallery modes (WGMs) of SuPs with the localised surface plasmon resonances (LSPRs) of a AuNP substrate. This interaction produces an increase in LSPR peak intensity of 10%. The luminescence and the WGM-to-non-resonant-luminescence ratio are both significantly increased (x2) under continuous wave excitation at the LSPR wavelength. Individual SuPs can also still act as microlasers when pulsed optically pumped on AuNPs outside the LSPR at 355 nm. These findings suggest this platform as a candidate for further development towards electrically driven cw optical energy sources, presenting us a solution processable route to device miniaturisation.