Enhancement of Raman scattering signal using photonic nanojet of portable and reusable single microstructures

Abstract

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.

Photonic nanojet mediated Raman enhancement: Vertical Raman mapping and simple ray matrix analysis

“…We believe the primary reason for the enhancement is the presence of the strongly localized electric field inside of the photonic nanojet on the shadow side of the sphere, as noted in other research, which leads to stronger Raman scattering. However, the influence of the NA is present, and there is a possibility that part of the mechanism is the increase of the NA, where the sphere allows better collection of scattered light, but further research is needed.…”

“…Geometrical aspects have been mostly investigated in terms of microsphere size and objective that has been used . Several researchers have achieved the highest enhancement positioning the focus of the incident beam so that the width of the beam covered the sphere . Alessandri et al have shown that the lower the numerical aperture (NA) of the objective is used, the higher the relative enhancement, while the incident beam was focused on top of the microsphere.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part XIII

“…Arya and co‐workers described the enhancement of Raman scattering intensity using a photonic nanojet of portable and reusable single lollipop‐shapted microstructures. These lollipop‐shapted microstructures are extremely useful for enhancing the Raman scattering and fluorescence signals of single or few molecules . Chen et al report a statistical analysis of cuboctahedral silver nanocrystals in Langmuir–Blodgett film SERS substrates.…”

“…These lollipop-shapted microstructures are extremely useful for enhancing the Raman scattering and fluorescence signals of single or few molecules. [108] Chen et al report a statistical analysis of cuboctahedral silver nanocrystals in Langmuir-Blodgett film SERS substrates. Their results help to identify important SERS substrate characteristics that influence the performance of a SERS substrate.…”

Numerical Study of Tunable Photonic Nanojets Generated by Biocompatible Hydrogel Core-Shell Microspheres for Surface-Enhanced Raman Scattering Applications

“…The generated photonic nanojet often has a sub-wavelength and high-intensity focus spot with a long effective length. Thus, the photonic nanojets are applied in several optical and photonic applications, including super-resolution white-light nanoscopy [22], optical waveguide [23], enhancement of Raman scattering signals [24,25,26,27,28,29], optical nano-patterning [30], detection of single nanoparticle and biomolecules [31], enhancement of backscattering of light [32], optical data-storage [33], optical forces [34], optical super-resolution photoacoustic microscopy [35], laser surgery [36], and photon fluorescence enhancement [37].…”