Enhanced Raman scattering by self-assembled silica spherical microparticles

Abstract

A technique was developed to achieve enhanced Raman scattering of the silicon photon modes using closely packed micro-and submicron silica spherical particles. Investigation on the particle-size dependence of Raman enhancement revealed that the strongest enhancement occurs when the particle diameter is equal to the spot size of the incident laser beam. Calculations using the OPTIWAVE™ software based on the finite difference time domain algorithm under the perfectly matched layer boundary conditions were carried out. The results showed that photonic nanojets are formed in the vicinity outside the particles along the propagation direction of incident light. It was found that the nanojets are confined to a length of 100 nm with a waist of 120 nm. The presence of the strongly localized electromagnetic fields within the nanojets accounts for the enhanced Raman scattering. This technique has potential applications both in modern and traditional areas of surface science such as surface oxidation, adhesion, corrosion, and catalytic processes, and many other areas in biology, chemistry, materials science, and microelectronics.

Enhancement of Raman scattering by individual dielectric microspheres

“…[7 -9] Taking advantage of this, an enhancement of optical spectral signals by dielectric microspheres is expected. Enhancements of two-photon fluorescence [13] and Raman scattering by dielectric microspheres [14,15] have been reported recently. Therein, solutions of spheres [13] or close-packed monolayer spheres [14,15] were used, wherein the interaction between neighboring spheres, such as multiple scattering, is unavoidable.…”

“…Enhancements of two-photon fluorescence [13] and Raman scattering by dielectric microspheres [14,15] have been reported recently. Therein, solutions of spheres [13] or close-packed monolayer spheres [14,15] were used, wherein the interaction between neighboring spheres, such as multiple scattering, is unavoidable. Accordingly, studies on the one-to-one correspondence between individual dielectric spheres and the enhanced optical spectra of samples (including bulk and surface samples) placed directly underneath the spheres compared to that without the spheres are needed.…”

Contrast enhancement using silica microspheres in coherent anti-Stokes Raman spectroscopic imaging

“…Figures 6(a) and 6(b) show the E-field distribution in a 2D view with and without a microsphere. It is known that microspheres can generate "photonic nanojets" with super small foci [23][24][25]. However, the divergent electromagnetic wave from a small area very close to the microspheres can be confined to a parallel propagation wave with a relatively narrow distribution with smaller full width at half maximum (FWHM) of the CARS signal wave, which increases the detection efficiency and enhance the imaging intensity.…”

Tailoring the Properties of Photonic Nanojets by Changing the Material and Geometry of the Concentrator

“…Besides applications in coupling light into integrated optical circuits and microscopy, nanojets could be used in two-photon fluorescence enhancement, maskless nano-patterning, detection of nano-particles, optical trapping and data storage. Another potential application of nanojets is the enhancement of Raman scattering [30] with enhancement factors in the order of 10000, being potentially used to any material. However, it should be mentioned that plasmonic devices can lead to enhancement of Raman scattering by factors above 1 million [31][32][33][34].…”