Cone-shell Raman spectroscopy (CSRS) for depth-sensitive measurements in layered tissue

Area of Science:

• Spectroscopy
• Optics
• Biomedical Engineering

Background:

• Raman spectroscopy is a powerful tool for chemical analysis.
• Current Raman spectroscopy methods often lack depth-resolution for subsurface analysis.
• Noncontact, depth-sensitive techniques are crucial for in vivo biological tissue analysis.

Purpose of the Study:

• To develop a novel depth-sensitive Raman spectroscopy system.
• To enable noncontact probing of subsurface layers in biological tissues.
• To demonstrate adjustable depth profiling capabilities.

Main Methods:

• Utilized a cone-shell excitation and detection configuration.
• Employed a 785 nm diode laser and three axicons for excitation.
• Designed a system for collecting Raman scattered light through a solid conic section.
• Varied probing depth by adjusting axicon separation in the excitation arm.

Main Results:

• The system achieved depth-sensitive Raman spectroscopy up to a few millimeters.
• Probing depth was successfully varied by adjusting axicon separation.
• Demonstrated recovery of Raman spectra from layers 2-3 mm beneath the surface in phantom and biological samples.
• Confirmed noncontact measurement capability with no sample arm adjustments.

Conclusions:

• The developed cone-shell Raman spectroscopy system offers effective depth-sensitive analysis.
• The system provides adjustable, noncontact probing of subsurface layers in biological samples.
• This technology has potential applications in biomedical diagnostics and research.