Visualizing surface plasmon polaritons by their gradient force

Area of Science:

• Plasmonics
• Near-field optics
• Nanophotonics

Background:

• Surface-plasmon-polariton (SPP) modes are crucial for nanoscale light manipulation.
• Direct visualization of SPP electric fields in the near-field is challenging.
• Existing methods often lack spatial resolution or direct field information.

Purpose of the Study:

• To present a novel method for direct near-field visualization of electric field distributions.
• To demonstrate the capability of imaging propagating surface-plasmon-polariton (SPP) modes.
• To establish a new tool for studying light-matter interactions at the nanoscale.

Main Methods:

• Utilizing a photo-induced gradient force exerted by the evanescent field.
• Employing a sharp, polarizable tip as a sensor.
• Implementing a photo-induced force microscope (PiFM) for detection.

Main Results:

• Successful imaging of propagating SPP modes was achieved.
• The method provides direct visualization of electric field distributions.
• High-resolution near-field images of SPPs on gold surfaces were obtained.

Conclusions:

• The developed PiFM-based method offers a powerful new approach for near-field optical imaging.
• This technique enables direct visualization of electric fields associated with SPPs.
• The findings contribute to a deeper understanding of plasmonic phenomena and nanoscale optics.