The manipulation of radiative properties of light emitters coupledwith surface plasmons is important for engineering new nanoscale optoelectronic devices, including lasers, detectorsand single photon emitters1, 2, 3, 4, 5, 6, 7, 8. 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 thermalizedexcitons2, 6, 9, 10, 11. 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–SiO2–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 >103 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.
At a glance
- Surface plasmon subwavelength optics. Nature 424, 824–830 (2003). , &
- Plasmonics for extreme light concentration and manipulation. Nature Mater. 9, 193–204 (2010). et al.
- Resonant optical antennas. Science 308, 1607–1609 (2005). , , , &
- Plasmonics for improved photovoltaic devices. Nature Mater. 9, 205–213 (2010). &
- Demonstration of a spaser-based nanolaser. Nature 460, 1110–1112 (2009). et al.
- Room-temperature sub-diffraction-limited plasmon laser by total internal reflection. Nature Mater. 10, 110–113 (2011). , , , &
- High-Q surface-plasmon-polariton whispering-gallery microcavity. Nature 457, 455–458 (2009). et al.
- Generation of single optical plasmons in metallic nanowires coupled to quantum dots. Nature 450, 402–406 (2007). et al.
- Surface-plasmon-enhanced light emitters based on InGaN quantum wells. Nature Mater. 3, 601–605 (2004). et al.
- Enhanced radiative emission rate and quantum efficiency in coupled silicon nanocrystal-nanostructured gold emitters. Nano Lett. 5, 1768–1773 (2005). , , &
- Enhancement and quenching of single-molecule fluorescence. Phys. Rev. Lett. 96, 113002 (2006). , &
- Oscillatory exciton emission in CdS. Phys. Rev. Lett. 20, 1344–1346 (1968). &
- Hot-electron relaxation in GaAs quantum wells. Phys. Rev. Lett. 55, 2359–2361 (1985). , , &
- Dynamics of exciton-polariton recombination in CdS. Phys. Rev. B 11, 3071–3077 (1975). &
- Hot-excitons in semiconductors. Phys. Status Solidi B 68, 9–42 (1975).
- Coherence length of excitons in a semiconductor quantum well. Phys. Rev. Lett. 89, 097401 (2002). , &
- Exciton-plasmon-photon conversion in plasmonic nanostructures. Phys. Rev. Lett. 99, 136802 (2007). , , , &
- Generation of molecular hot electroluminescence by resonant nanocavity plasmons. Nature Photon. 4, 50–54 (2010). et al.
- Plasmon lasers at deep subwavelength scale. Nature 461, 629–632 (2009). et al.
- Variable temperature spectroscopy of as-grown and passivated CdS nanowire optical waveguide cavities. J. Phys. Chem. A 115, 3827–3833 (2011). et al.
- Exciton spectrum of cadmium sulfide. Phys. Rev. 116, 573–582 (1959). &
- Hot-excitons and exciton excitation spectra. J. Phys. Chem. Solids 31, 2595–2606 (1970). , , &
- Lattice dynamics of wurtzite: CdS. II. Phys. Rev. B 1, 595–603 (1970). , &
- Hot-exciton luminescence in CdSe crystals. Phys. Status Solidi B 59, 551–560 (1973). , , &
- Hot-exciton luminescence in ZnTe/MnTe quantum wells. Phys. Rev. B 43, 9354–9357 (1991). et al.
- Semiconductor nanowires: Optics and optoelectronics. Appl. Phys. A 85, 209–215 (2006). &
- 2007). Plasmonics: Fundamentals and Applications (Springer,
- Spontaneous emission probabilities at radio frequencies. Phys. Rev. 69, 681 (1946).
- 124–224 (Oxford, 1986). Chemical Applications of Ultrafast Spectroscopy
- Optical constants of noble metals. Phys. Rev. B 6, 4370–4379 (1972). &
- 1998). Handbook of Optical Constants of Solids (Academic,