We report the enhancement of Raman scattering signal for the first time using photonic nanojet of a lollipop‐shaped microstructure (LMS) fabricated with the help of a nanosecond CO2 laser. The LMS consists of a dielectric microsphere attached to a long stem/tapered fiber. The enhancement was achieved by focusing the incident laser light on sample surface through the microsphere of LMS. The experimentally observed enhancement was found to be comparable with that obtained from commercial microspheres that are not attached to any stems. The value of enhancement was found to increase with the microsphere diameter. The dielectric stems/tapered fibers alone of the LMS are found not efficient for enhancing the Raman scattering signals. In contrast to the commercial microspheres, the fabricated LMSs are easy to handle, portable, and reusable. Also, unlike commercial microspheres, these LMSs allow the enhancement of Raman scattering without modifying the surface of substrates containing sample. Hence, these LMSs are extremely useful in the case of photonic nanojet‐mediated surface‐enhanced Raman scattering and fluorescence techniques for enhancing the Raman scattering and fluorescence signals of single/few molecules, respectively.
Herein, we report a finite element method simulated near-field spectra of single nanoshell dimers placed over nano-and microscale dielectric substrates. The simulations have been carried out on an individual basis for the top and bottom illuminated nanodimers with a plane wave and a focused Gaussian beam. Only one peak has been observed in the near-field spectra of free-standing and nano-scale substrate-supported nanodimers, due to the constructive coupling of fundamental modes of nanoshells at the nanogap. The wavelength location of the peak has been slightly red shifted in the presence of the nanoscale dielectric substrate. But, the obtained spectra have been found nearly independent with the type and direction of propagation of excitation light (k exc). However, multiple peaks have been noticed in the near-field spectra in the presence of microscale substrates due to the constructive coupling of lower as well as higher order modes (multipolar modes) of nanoshells at the nanogap. In contrast, the near-field spectra have been found sensitive to all dimensions of the substrate, the type of excitation light, and the direction of (k exc). Moreover, the far-field scattering spectra of a microscale substrate supported nanodimers have also been found sensitive to the direction of (k exc).
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