Spectral line

Quantum mechanics

Materials science

Mode volume

Scattering

Operating system

Computer science

Fiber optic sensor

Light scattering

Physical chemistry

Polarization (electrochemistry)

Thermodynamics

Physics

Nanotechnology

Dielectric

Optics

Astronomy

Molecular physics

Resonator

Composite material

Fiber

Plasmon

Chemistry

Graded-index fiber

Optoelectronics

Human–computer interaction

Mode (computer interface)

Volume (thermodynamics)

Nanoscale Advances

Confining and controlling light in extreme subwavelength scales are tantalizing tasks. In this work, we report a study of individual plasmonic film-coupled nanostar resonators where polarized plasmonic optical modes are trapped in ultrasmall volumes. Individual gold nanostars, separated from a flat gold film by a thin dielectric spacer layer, exhibit a strong light confinement between the sub-10 nm volume of the nanostar's tips and the film. Through dark field scattering measurements of many individual nanostars, a statistical observation of the scattered spectra is obtained and compared with extensive simulation data to reveal the origins of the resonant peaks. We observe that an individual nanostar on a flat gold film can result in a resonant spectrum with single, double or multiple peaks. Further, these resonant peaks are strongly polarized under white light illumination. Our simulation data revealed that the resonant spectrum of an individual film-coupled nanostar resonator is related to the symmetry of the nanostar, as well as the orientation of the nanostar relative to its placement on the gold substrate. Our results demonstrate a simple new method to create an ultrasmall mode volume and polarization sensitive plasmonic platform which could be useful for applications in sensing or enhanced light-matter interactions.

Small mode volume plasmonic film-coupled nanostar resonators