Fluorescence suppression in Raman spectroscopy using a time-gated CMOS SPAD

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Photonics

Background:

• Fluorescence is a common interfering background signal in Raman spectroscopy.
• Traditional Raman spectroscopy methods struggle to effectively suppress fluorescence.
• Accurate spectral analysis is often hindered by overwhelming fluorescence signals.

Purpose of the Study:

• To develop and demonstrate a Raman spectroscopy technique for significant fluorescence background suppression.
• To improve the signal-to-noise ratio in Raman spectra.
• To enable clearer analysis of Raman scattering from fluorescent samples.

Main Methods:

• Utilized a high-power, short-pulsed laser (65W, 300ps) for sample excitation.
• Employed a CMOS SPAD detector and time-to-digital converter to measure photon arrival times relative to the laser pulse.
• Recorded sample response selectively for photons coinciding with the laser pulse and applied corrections for residual fluorescence tails.

Main Results:

• Demonstrated substantial suppression of fluorescence background in Raman spectra of olive oil.
• Showcased the effectiveness of time-gated detection in isolating Raman signals from fluorescence.
• Achieved further baseline correction using measured fluorescence decay tails.

Conclusions:

• The developed time-resolved Raman spectroscopy technique effectively suppresses fluorescence.
• This method significantly enhances spectral quality for samples with high fluorescence.
• The technique offers a viable solution for analyzing complex samples in various scientific fields.