Multi-Photon Counting in Raman Spectroscopy By Signal Processing of Photomultiplier Tube Response

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Researchers at Purdue University have developed a new method to enable multi-photon counting in Raman spectroscopy by sub-nanosecond digital signal processing of photomultiplier tube (PMT) response to laser pulses. The two-fold hardware and software system can be implemented in research and industry applications for nondestructive chemical and physical analysis. The setup allows for rapid classification and determination of yield for a variety of samples in a broad range of low and high concentrations with enhanced speed and sensitivity over traditional Raman techniques. In addition, this approach can decrease total experiment times and improve noise rejection. Currently Raman spectroscopy considers photon arrivals as binary events that are accessed by a single threshold. Purdue researchers have focused on the potential for multiple photons to strengthen signals via high-speed data acquisition and multi-threshold digital signal processing (DSP). Their software features an algorithm for multi-photon counting and hardware to record PMT output, considering amplitude and time of as many photons as possible. In testing with each of aqueous nitrate, isopropanol, and rhodamine 6G, sensitivity was increased by 2.0-, 2.0-, and 3.1-fold respectively from traditional Raman spectroscopy analysis. Calibration curves showed improved accuracy, as well.

-Multi-Photon Counting
-Stronger Signal
-Allows for Broader Low/High Concentration Range for Sample Analysis
-Decreases Experimentation Time
-Improves Noise Rejection
-Increases Spectroscopic Sensitivity on Average 2- to 3-Fold

Potential Applications:
-Raman Spectroscopy
-Wireless Sensing Systems
-Research Analysis and Sampling

Technology Validation: In three unique aqueous solutions, the sensitivity of the new system developed by Purdue researchers was compared to current Raman spectroscopy systems. An increase by 2- to 3-fold in sensitivity was achieved for each.
Apr 27, 2021
United States
Purdue Office of Technology Commercialization
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West Lafayette, IN 47906

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