Close to-unity Raman beta issue underpins excessive sensitivity

Raman scattering1 is a potent method for unambiguously figuring out the presence of tiny portions of various substances, because it accesses the wealthy and distinctive spectral fingerprint of a given substance’s vibrational spectrum whereas working within the optical vary, the place each highly effective laser sources and delicate detectors can be found. Nonetheless, being a 3rd order nonlinear course of, Raman scattering suffers from very low effectivity, limiting sensitivity. Completely different strategies have been used to boost sensitivity of Raman detection. Amongst them is utilizing resonant Raman scattering2, however that requires a pump laser to be tuned near the molecule’s digital transition, which isn’t all the time potential. A strong enhancement method broadly used right this moment is floor enhanced Raman scattering3 (SERS) the place the pump area is strongly enhanced in a sub-wavelength measurement area (or ‘sizzling spot’) close to a nanostructured metallic floor. As well as, in SERS the density of photon states on the scattered wavelength is enhanced, inflicting additional effectivity enhancement as a result of Purcell impact.

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