Surface-plasmon mediated total absorption of light into silicon

Area of Science:

• Optics and Photonics
• Materials Science
• Plasmonics

Background:

• Efficient light absorption in silicon is crucial for optoelectronic devices.
• Surface plasmon polaritons (SPPs) offer a pathway to enhance light-matter interactions at metal-dielectric interfaces.

Purpose of the Study:

• To investigate surface-plasmon mediated total absorption of light into a silicon substrate.
• To quantify the enhancement of absorption via SPP excitation on an gold (Au) grating on silicon (Si).

Main Methods:

• Experimental excitation of surface-plasmon polaritons (SPPs) on an Au grating on Si.
• Measurement of reflection and phase spectra.
• Rigorous numerical simulations to analyze light propagation and absorption mechanisms.
• Development of an analytic model of a dissipative quasi-bound resonator.

Main Results:

• Achieved near-total light absorption into the silicon substrate mediated by SPPs.
• Observed absorption rates nearly 10 times greater than the ohmic damping rate in the gold film.
• Simulations confirmed resonant enhancement of light diffraction into the silicon substrate with negligible reflection and ohmic absorption in gold.
• Established a quantitative relation between peak absorbance and reflection phase change, indicating resonant interference.

Conclusions:

• Surface-plasmon polaritons provide a highly effective mechanism for enhancing light absorption in silicon.
• The findings offer a generalizable model for resonant absorption enhancement in plasmonic systems.
• This approach has potential applications in improving the efficiency of silicon-based optoelectronic devices.