Time-resolved photon counting Fourier-transform micro-spectroscopy enables simultaneous Raman and fluorescence...

Area of Science:

• Spectroscopy
• Photonics
• Analytical Chemistry

Background:

• Time-gated Raman spectroscopy has limitations including narrow spectral range and low spectral resolution.
• Simultaneous acquisition of Raman and fluorescence lifetime images is challenging.

Purpose of the Study:

• To develop a Fourier-transform photon counting spectroscopy platform.
• To overcome limitations of existing time-gated Raman spectroscopy methods.
• To simultaneously acquire Raman and fluorescence lifetime images.

Main Methods:

• A Mach-Zehnder interferometer with a high-accuracy linear motor stage was utilized.
• Photon-counting avalanche diodes and time-tagged acquisition were employed.
• Photons were sorted based on coarse arrival time (50 ns steps) and fine arrival time (80 ps resolution).

Main Results:

• Achieved a time resolution of 547 ps.
• Obtained a wide spectral range of -1000 to 10,000 cm^-1 Raman shift.
• Reached a high spectral resolution of 0.05 cm^-1.
• Successfully separated Raman signals (during excitation pulse) from fluorescence signals (after excitation pulse).

Conclusions:

• The developed Fourier-transform photon counting spectroscopy platform effectively addresses limitations in time-gated Raman spectroscopy.
• The instrument demonstrates capability for simultaneous Raman and fluorescence signal acquisition and separation.
• Validated using fluorescently coated silicon wafers and microspheres.