Ultrastrong coupling between nanoparticle plasmons and cavity photons at ambient conditions

Understand

Ultrastrong coupling is a distinct regime of electromagnetic interaction that enables a rich variety of intriguing physical phenomena.

• Traditionally, this regime has been reached by coupling intersubband transitions of multiple quantum wells, superconducting artificial atoms, or two-dimensional electron gases to microcavity resonators.
• However, employing these platforms requires demanding experimental conditions such as cryogenic temperatures, strong magnetic fields, and high vacuum.
• Here, we use plasmonic nanorods array positioned at the antinode of the resonant optical Fabry-P\'erot microcavity to reach the ultrastrong coupling (USC) regime at ambient conditions and without the use of magnetic fields.