Description
Raman spectroscopy is a powerful optical spectroscopy technique that provides a molecular-level fingerprint through inelastic light scattering. However, Raman signals are often weak and obscured by the presence of a strong fluorescent background. Raman scattering arises from an interaction with a virtual state, which is very short-lived. In contrast, fluorescence occurs through excited-state exponential decay with lifetime typically longer than the Raman process. As a result, precisely time gating the collected signal can distinguish between the two phenomena. An early time gate preferentially selects Raman photons and suppresses the fluorescence background, thereby enhancing the Raman signal contrast. This technique requires time-correlated photon counting using detectors with high sensitivity and precise timing. Here, we show that a high-efficiency Superconducting Nanowire Single-Photon Detector (SNSPD) offers a significantly lower timing jitter than the more ubiquitous Single-Photon Avalanche Diode (SPAD). In turn, this leads to an increased discrimination between the Raman and fluorescence signals and an improved signal to noise ratio (SNR).
We apply this technique to a range of samples with significant fluorescence background to demonstrate the advantage of an SNSPD over a SPAD. Due to the superior noise floor and jitter of the SNSPD, we observe an improvement of the SNR by a factor of up to 4.0 for Raman peaks from samples of olive oil, sesame oil and yeast. These insights will give an improved limit of detection for trace contaminants in low-yield Raman regimes.
| I am the presenting author | Yes |
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