Observation of long range surface plasmon decay length by optical second harmonic generation

Area of Science:

• Plasmonics
• Nonlinear Optics
• Surface Science

Background:

• Long-range surface plasmon polaritons (LRSPPs) are surface electromagnetic waves that propagate along interfaces.
• Understanding their propagation characteristics, including spatial decay, is crucial for applications in sensing and optoelectronics.
• Surface roughness is a known factor that can influence wave propagation.

Purpose of the Study:

• To experimentally observe and quantify the spatial decay of long-range surface plasmon modes.
• To investigate the influence of surface roughness on the propagation of these modes.
• To compare experimental results with theoretical predictions.

Main Methods:

• Excitation of surface plasmon modes at 1.06 micrometers using prism coupling.
• Utilizing a multilayer structure: quartz substrate, thin silver film, and index-matched liquid.
• Analysis of the reflected second harmonic generation profile to determine the decay length.

Main Results:

• Observation of the spatial decay of the long-range surface plasmon mode.
• Determination of a decay length of 0.8 mm from the second harmonic profile asymmetry.
• Experimental decay length was found to be approximately three times smaller than theoretically predicted values.

Conclusions:

• The spatial decay of long-range surface plasmon modes was successfully observed.
• Surface roughness scattering plays a significant role in reducing the propagation distance of LRSPPs.
• Experimental findings highlight the importance of surface quality in plasmonic devices.