Time-resolved Raman spectroscopy using a CMOS SPAD array to remove fluorescent and fibre Raman backgrounds

Area of Science:

• Spectroscopy
• Optical Engineering
• Materials Science

Background:

• Raman spectroscopy faces challenges with weak signals, fluorescence interference, and fiber-induced backgrounds.
• Existing methods struggle to efficiently detect faint Raman signals while mitigating noise sources.

Purpose of the Study:

• To develop a compact optical system for enhanced Raman signal detection.
• To suppress background fluorescence and fiber-induced signals using time-gating techniques.
• To enable miniaturized single-fiber Raman probes for remote sensing applications.

Main Methods:

• Utilized a 512-pixel complementary-metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) line sensor array.
• Integrated on-chip timing electronics for precise signal detection and time-gating.
• Demonstrated functionality in free-space and through a 1m 50µm core multimode fiber.

Main Results:

• Achieved improved signal enhancement with significantly shorter measurement times (30 s) in free space.
• Successfully suppressed fiber background noise for remote detection of samples like paracetamol.
• Validated the system's capability for miniaturized single-fiber Raman probe development.

Conclusions:

• The developed CMOS SPAD sensor array effectively enhances Raman signal detection and background suppression.
• Time-gating is a viable strategy for mitigating fluorescence and fiber-induced interference in Raman spectroscopy.
• This technology paves the way for compact, high-performance fiber-based Raman probes for diverse applications.