Inverse spatially-offset Raman spectroscopy using optical fibers: An axicon lens-free approach.

Area of Science:

• Spectroscopy
• Optical Engineering
• Materials Science

Background:

• Inverse Spatially Offset Raman Spectroscopy (I-SORS) is used for analyzing layered, scattering samples.
• Traditional I-SORS methods require bulky axicons and component movement, limiting probe size and practicality.
• A need exists for compact, versatile I-SORS probes for in situ measurements.

Purpose of the Study:

• To develop a novel, compact I-SORS probe design.
• To overcome limitations of traditional axicon-based I-SORS configurations.
• To enable depth-sensitive Raman measurements in challenging sample types.

Main Methods:

• Implemented a new I-SORS scheme using two multi-mode optical fibers for ring illumination and point collection.
• Designed a fiber-optic configuration eliminating the need for physical movement of optical components.
• Developed a compact, pencil-sized probe suitable for in situ applications.

Main Results:

• Successfully demonstrated a novel I-SORS implementation without requiring component movement.
• Achieved a compact probe design, overcoming the limitations of axicon-based systems.
• The fiber-optic approach is well-suited for creating narrow-diameter I-SORS probes.

Conclusions:

• The proposed fiber-optic I-SORS scheme offers a significant advancement for developing compact, practical probes.
• This method facilitates in situ, depth-sensitive Raman analysis of layered, turbid samples.
• The design overcomes previous limitations, paving the way for wider I-SORS applications.