Ultra-low background Raman sensing using a negative-curvature fibre and no distal optics

Area of Science:

• Spectroscopy
• Materials Science
• Optical Engineering

Background:

• Measuring Raman spectra via optical fibers is challenging due to high intrinsic fiber material Raman scatter.
• Existing solutions, like multiple fibers and distal optics, are complex and bulky.

Purpose of the Study:

• To demonstrate the use of novel hollow-core negative-curvature fibers (NCFs) for Raman and surface-enhanced Raman spectroscopy (SERS) sensing.
• To overcome the limitations of conventional solid fibers and bulky optical setups.

Main Methods:

• Utilized single hollow-core negative-curvature fibers (NCFs) for light transmission and signal collection.
• Transmitted 785-nm laser pump light through the NCF and collected back Raman spectra.
• Compared NCF performance against conventional solid fibers, assessing background emission and collection efficiency.

Main Results:

• NCFs exhibited at least 1000x lower background Raman emission compared to conventional solid fibers.
• Maintained equivalent Raman signal collection efficiency.
• Successfully measured weak Raman and SERS signals from distal samples without distal optics.

Conclusions:

• Novel NCFs offer a simplified, compact, and effective solution for Raman and SERS sensing.
• The reduced silica background in NCFs enables detection of weak signals previously masked by fiber emission.
• The absence of distal optics and small probe diameter (<0.25 mm) open new application possibilities in optical sensing.