Low-Background Tip-Enhanced Raman Spectroscopy Enabled by a Plasmon Thin-Film Waveguide Probe

Area of Science:

• Nanophotonics
• Surface Science
• Spectroscopy

Background:

• Direct-illumination Tip-Enhanced Raman Spectroscopy (TERS) suffers from high background noise from fluorescence and far-field signals.
• This limits TERS applications for fluorescent materials or bulk samples not on suitable substrates.
• Achieving high signal contrast remains a challenge for commercial TERS instruments.

Purpose of the Study:

• To develop an indirect-illumination TERS probe to overcome background limitations.
• To enable high-resolution, low-background TERS measurements.
• To enhance the commercial viability and application scope of TERS technology.

Main Methods:

• Developed an indirect-illumination TERS probe utilizing a thin-film waveguide.
• Focused laser illumination on a waveguide interface, distant from the TERS signal generation region.
• Generated stable surface plasmon polaritons accumulated at the probe tip to create a confined hotspot.

Main Results:

• Acquired TERS spectra with significant contrast from a diamond plate using the new probe.
• Demonstrated excellent TERS signal stability and a long operational lifetime.
• Achieved good spatial resolution in TERS measurements, confirming the hotspot's confinement.

Conclusions:

• The indirect-illumination TERS probe effectively reduces background noise and enhances signal contrast.
• This technique offers stable, high-resolution chemical analysis capabilities for challenging samples.
• The developed probe shows significant commercial potential for advancing TERS technology.