Probing optical resonances of silicon nanostructures using tunable-excitation Raman spectroscopy

Area of Science:

• Nanophotonics
• Materials Science
• Spectroscopy

Background:

• High refractive index optical materials confine light strongly at the nanoscale.
• Probing the optical near field within these nanostructures is challenging with current methods.

Purpose of the Study:

• To develop a novel technique for detecting resonance-induced near-field enhancements in silicon nanostructures.
• To establish Raman scattering as a method for nanoscale optical characterization and quality control.

Main Methods:

• Utilized a wavelength-tunable laser Raman setup to excite silicon thin films and nanodisk arrays.
• Exploited the link between Raman scattering and stored electric energy to detect near-field enhancements.
• Compared Raman response on and off resonance to quantify near-field effects.

Main Results:

• Identified Fabry-Pérot and Mie resonances in silicon nanostructures via tunable-excitation Raman spectroscopy.
• Demonstrated that Raman spectroscopy can measure optical near-field enhancement.
• Showcased the ability of Raman spectroscopy to detect fabrication imperfections in silicon nanodisk arrays.

Conclusions:

• Tunable-excitation Raman spectroscopy serves as a complementary far-field technique for nanoscale characterization.
• This method enables all-optical quality control of metasurfaces by detecting fabrication defects.