Chiral Plasmonic Fiber Tip-Enhanced Raman Nanospectroscopy

Area of Science:

• Plasmonics
• Spectroscopy
• Nanotechnology

Background:

• Tip-enhanced Raman spectroscopy (TERS) faces challenges with excitation efficiency and background noise.
• This limits sensitivity and obscures higher-order Raman transitions, hindering nanoscale analysis.

Purpose of the Study:

• To overcome TERS limitations by developing a novel chiral plasmonic fiber tip (CPFT).
• To enhance electric-field intensity and gradient at the tip apex for improved spectroscopy.

Main Methods:

• Fabrication of CPFT using fused tapering and rotational stretching.
• Internal excitation of the CPFT by the fiber vector fundamental mode.
• Utilizing structural asymmetry to achieve constructive interference of surface plasmon polaritons.

Main Results:

• Achieved a 4-fold higher signal-to-noise ratio compared to conventional side excitation.
• Successfully visualized dark-state Raman modes, including electric-quadrupole and magnetic-dipole transitions.
• Demonstrated enhanced electric-field intensity and gradient at the tip hotspot.

Conclusions:

• The CPFT design effectively amplifies electromagnetic fields and suppresses background noise in TERS.
• This approach offers a strategy for high-contrast nanoscale spectroscopy.
• Paves the way for next-generation, highly sensitive, low-noise TERS systems.