Imaging the dark emission of spasers

Area of Science:

• Optics and Photonics
• Nanotechnology
• Plasmonics

Background:

• Spasers are nanoscale lasers operating below the diffraction limit.
• Their applications include sensing, imaging, and optical communication.
• Spaser emission is typically 'dark' and evanescent, making it difficult to study.

Purpose of the Study:

• To directly image the intrinsic surface plasmon emission of spasers.
• To provide evidence for the spaser's coherent surface plasmon amplification mechanism.
• To explore the potential for high coupling efficiency in spaser devices.

Main Methods:

• Simultaneous imaging of spaser emission in spatial, momentum, and frequency domains.
• Utilizing a nanowire spaser for experimental demonstration.
• Theoretical analysis of coupling efficiency based on nanowire diameter.

Main Results:

• Direct visualization of spaser surface plasmon emission was achieved.
• A nanowire spaser demonstrated a 74% coupling efficiency to plasmonic modes.
• Theoretical calculations suggest near-100% efficiency for sub-50 nm nanowires.

Conclusions:

• The study provides direct evidence of spasers acting as coherent surface plasmon amplifiers.
• The revealed "dark" emission is crucial for understanding spaser operation.
• Optimized spaser designs could lead to highly efficient nanoscale light sources.