Ultrasmall mode volume plasmonic nanodisk resonators

Area of Science:

• Plasmonics and Nanophotonics
• Optical Cavities
• Metamaterials

Background:

• Metal-insulator-metal (MIM) plasmons offer unique optical properties.
• Nanoscale resonators are crucial for controlling light-matter interactions.
• Achieving ultrasmall cavity mode volumes is a key challenge in nanophotonics.

Purpose of the Study:

• To investigate resonant modes in nanoscale disk resonators with MIM plasmons.
• To demonstrate the capability of these cavities for achieving ultrasmall mode volumes.
• To explore their potential for enhanced spontaneous emission and lasing.

Main Methods:

• Fabrication of Ag/SiO2/Ag MIM disk structures using thin-film deposition and focused ion beam milling.
• Characterization of cavity-mode field distributions via cathodoluminescence imaging spectroscopy.
• Comparison of experimental results with boundary element calculations.

Main Results:

• Observed lowest order mode (m = 1, n = 1) in the visible spectrum for cavities with diameters d = 65-140 nm.
• Demonstrated a cavity quality factor (Q) of 16 for a 105 nm diameter cavity.
• Achieved an ultrasmall mode volume of 0.00033λ₀³ and a Purcell factor of 900.

Conclusions:

• Nanoscale disk resonators with MIM plasmons provide versatile platforms for ultrasmall cavity mode volumes.
• The observed mode resembles that of plasmonic particle dimers, linking localized and traveling plasmon cavities.
• These resonators are promising for enhanced spontaneous emission and lasing applications.