Tailoring hot-exciton emission and lifetimes in semiconducting nanowires via whispering-gallery nanocavity plasmons

Abstract

The manipulation of radiative properties of light emitters coupled with surface plasmons is important for engineering new nanoscale optoelectronic devices, including lasers, detectors and single photon emitters. However, so far the radiative rates of excited states in semiconductors and molecular systems have been enhanced only moderately, typically by a factor of 10-50, producing emission mostly from thermalized excitons. Here, we show the generation of dominant hot-exciton emission, that is, luminescence from non-thermalized excitons that are enhanced by the highly concentrated electromagnetic fields supported by the resonant whispering-gallery plasmonic nanocavities of CdS-SiO(2)-Ag core-shell nanowire devices. By tuning the plasmonic cavity size to match the whispering-gallery resonances, an almost complete transition from thermalized exciton to hot-exciton emission can be achieved, which reflects exceptionally high radiative rate enhancement of >10(3) and sub-picosecond lifetimes. Core-shell plasmonic nanowires are an ideal test bed for studying and controlling strong plasmon-exciton interaction at the nanoscale and opens new avenues for applications in ultrafast nanophotonic devices.

Optical antenna enhanced spontaneous emission

“…Metal structures have also been used to enhance the spontaneous emission rate, such as by coupling excited material to flat surface plasmon waves (21)(22)(23)(24)(25)(26)(27)(28). Flat metal surfaces are far from ideal antennas, resulting in low radiation efficiencies and large ohmic losses.…”

Tailoring the Lasing Modes in Semiconductor Nanowire Cavities Using Intrinsic Self-Absorption

“…[11][12][13] Recent groundbreaking work on utilizing semiconductor NW cavities to compensate the damping loss and amplify the collective electron oscillations in plasmon nanocavities has kindled even greater interests in this field. 2,13,14 For practical applications, the ability to tailor the NW cavity mode is essential for developing multi-color miniaturized lasers, and critical for optimizing the resonant energy transfer between the cavity and the coupled system. 15 For a II-VI or III-V NW Fabry-Pé rot cavity, it is generally accepted that the output laser wavelength is determined by the bandgap of semiconductor NW.…”

Enhanced second-harmonic generation from metal-integrated semiconductor nanowires via highly confined whispering gallery modes

“…Hybrid systems, for example, nanoscale nonlinear dielectrics coupled to metallic structures, utilize the local-field enhancement of SPRs to enhance SHG, but suffer from highOhmic losses at the metal-dielectric interface, and poor spatial overlap with the nonlinear material 23 , and may not be used for waveguiding applications. For example, sub-100 nm dielectric nanoparticles coupled with plasmonic cavities have demonstrated large enhancements of the SHG signal based on SPRs 24 , in which the enhanced field on the surface can significantly overlap with the nonlinear dielectrics.…”

“…However, for nanostructures such as NW with dimensions smaller than the wavelength of the incident light, WGMs are loosely confined and exhibit high loss 25 , and hence not very useful for nonlinear optical applications such as SHG. Furthermore, use of SPRs for the enhancement of the SHG signal for these intermediate sized particles (4150 nm) or NWs 23 may not be too efficient because of the lower overlap of the surface-plasmon modes with the bulk of the nonlinear material.…”