Observations of backscattering effects in second-harmonic generation from a weakly rough metal surface

Area of Science:

• Condensed matter physics
• Surface science
• Optics

Background:

• Surface plasmon polaritons (SPPs) are collective electron oscillations on metal surfaces.
• Second-harmonic generation (SHG) is a nonlinear optical process where light frequency doubles.
• Surface roughness can mediate the coupling of light to SPPs.

Purpose of the Study:

• To experimentally investigate the angular distribution of diffusely scattered second-harmonic light.
• To understand the role of weak random surface roughness in nonlinear light scattering.
• To explore the coupling of incident light to surface plasmon polaritons at the second harmonic frequency.

Main Methods:

• Experimental observation of scattered light from a silver surface.
• Utilizing a silver surface with controlled weak random roughness.
• Analysis of the angular distribution of second-harmonic light.

Main Results:

• Diffusely scattered second-harmonic light was observed from a rough silver surface.
• Surface roughness successfully coupled the incident wave to counterpropagating surface plasmon polaritons (SPPs) at the second harmonic.
• A distinct minimum in the angular distribution was observed in the backscattering direction, contrary to expectations of enhancement.

Conclusions:

• Weak random surface roughness can excite surface plasmon polaritons (SPPs) at the second harmonic frequency.
• The observed minimum in backscattering suggests complex scattering dynamics or SPP propagation effects.
• Further investigation is needed to fully elucidate the mechanisms behind the suppressed backscattering in this configuration.