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Direct Comparison of Hyperspectral Stimulated Raman Scattering and Coherent Anti-Stokes Raman Scattering Microscopy for Chemical Imaging
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Time-gated Raman spectroscopy using a 3D-stacked back-side illuminated CMOS SPAD array
Optics Letters
|December 1, 2025
Summary
This study demonstrates a novel back-side illuminated (BSI) single photon avalanche diode (SPAD) array for time-resolved Raman spectroscopy. The Atlas sensor achieves high count rates and precise timing, enabling microsecond spectral peak observation.
Area of Science:
- Photonics and Spectroscopic Imaging
- Advanced Semiconductor Devices
- CMOS Sensor Technology
Background:
- Single photon avalanche diodes (SPADs) are crucial for low-light imaging.
- Back-side illuminated (BSI) technology enhances light detection efficiency.
- Time-resolved sensing is vital for spectroscopic applications.
Purpose of the Study:
- To characterize the temporal response of the Atlas BSI SPAD array.
- To demonstrate the first use of a BSI SPAD array for time-resolved Raman spectroscopy.
- To evaluate the performance of the Atlas sensor for spectroscopic applications.
Main Methods:
- Characterization of the temporal response of the 128x128 BSI SPAD array.
- Implementation of time-resolved Raman spectroscopy using the Atlas sensor.
- Performance comparison with a front-side illuminated SPAD array (RaII).
Main Results:
- Achieved a mean time resolution of 1.44 ns (FWHM) and a timing offset of ~153 ps.
- Observed a 10.7x improvement in count rate compared to the RaII sensor.
- Successfully detected Raman spectral peaks with microsecond exposures.
Conclusions:
- The Atlas BSI SPAD array demonstrates significant advantages for spectroscopy.
- 3D-stacked BSI CMOS technology enables high-performance time-resolved sensing.
- This work paves the way for advanced spectroscopic imaging applications.
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