Enhancement of Raman scattering by individual dielectric microspheres

Abstract

Enhanced Raman scattering (ERS) from bulk Si and surface brilliant cresyl blue (Bcb) molecules was investigated by individual polystyrene (PS) microspheres placed on top of the samples. It is revealed that the Raman signal depends both on the microsphere size and the numerical aperture (NA) of the collection lens, and a maximum signal enhancement of ∼11-and 40-fold for Si and Bcb is observed, respectively, showing strong ERS effect. The different ERS behavior was elucidated by electromagnetic simulations using the finite element method. The present work also provides information on individual dielectric sphere for applications in microscopy, spectroscopic imaging and improvement, etc.

Individual Ag Nanowire Dimer for Surface-Enhanced Raman Scattering

“…A half-wave plate was introduced to change the polarization angle θ of the incident laser. Unless otherwise stated, the power of the incident laser was kept at about 20 μW in the experiments to minimize the photo-dissociation/photo-damage of BCB while the acquisition time of each single spectrum was 10 s. Determined from a scanning knife-edge method, the beam size of the incident laser was 500 nm [23]. Considering the localized excitation of the NWs, the SERS behaviors of points P1 and P3 are representative of that of the body and tip of an individual AgNW monomer, respectively, while P2 is representative of that of the body of an individual AgNW dimer.…”

Photonic jet generated by spheroidal particle with Gaussian-beam illumination

“…More recently, the feasibility of using a photonic jet to design sensors with high spatial resolution [26][27][28], tools for precision cell surgery and tumor detection [29,30], and optical tweezers [3,31], as well as to develop optical data storage devices with ultrahigh density of information recording [32,33] and technologies of directwrite nanopatterning [34,35], was also reported. In addition, the photonic jet effects have been used in Raman spectroscopy [36][37][38], fluorescence enhancement [39][40][41][42][43], and superresolution optical microscopy [44]. Besides, it has been shown that a dielectric microsphere illuminated by a focused Gaussian beam can outperform classical microscope systems, and significantly enhance the fluorescence emission from a single emitter [45].…”

Raman scattering enhancement by dielectric spheres

“…Note the thickness of the excited volume is assumed to be equal both in the presence and absence of a sphere and thus cancel. Thus, not surprising, while silica spheres on Si [15] have an order of magnitude shorter nanojet compared to polystyrene spheres on Si [16] (for similar experimental conditions), the former has onlỹ 30% less EF value. In addition, the same argument explains also why the EF for sphere/Si structures are very similar in magnitude and have the same dependence on d as sphere/Si/M structures.…”

“…[13] However, when light in the form of a Gaussian beam (514 nm) is focused on silica spheres supported on Si, a unimodal ED distribution with a FWHM of~120 nm is reported. [15,16] For d values larger than 2-3 mm, the ED distribution develops side peaks, which grow and becomes dominant (see ED distribution for d = 5 mm in Fig. 2).…”