Photonic nanojet-mediated SERS technique for enhancing the Raman scattering of a few molecules

We report a two-step enhancement of Raman scattering signal () of a few dye molecules. In the first step, high-quality surface-enhanced Raman scattering (SERS) substrates have been used. The SERS substrates were fabricated by direct current sputtering of Au followed by thermal annealing. The role of thermal annealing of the SERS substrates and numerical aperture of Raman microscopic objective lens on the enhancement has been studied for optimizing the enhancement in the SERS technique. In the second step, the value of obtained with conventional SERS technique has been improved significantly with the help of photonic nanojet (PNJ) of an optical microsphere (PNJ-mediated SERS technique). The signal to noise ratio and reproducibility of the experimental results have been found to be very high. Based on our theoretical simulations on PNJ, a few suitable parameters have been proposed for obtaining better enhancement using this technique. To the best of our belief, this report will enable the SERS community to improve value with ease. Copyright (c) 2016 John Wiley & Sons, Ltd.