title: Experimental confirmation at visible light wavelengths of the backscattering enhancement phenomenon of the photonic nanojet.
abstract: We report what we believe is the first experimental confirmation at visible light wavelengths of the backscattering enhancement phenomenon of the photonic nanojet. A specially designed sample stage consisting of a multilayered sandwich of glass, solid polydimethylsiloxane (PDMS), and liquid PDMS, permitted the precise positioning of a gold nanoparticle of diameter between 50 and 100 nm within the nanojet emitted by a 4.4 μm diameter BaTiO(3) microsphere embedded within the PDMS. We determined that, when the gold nanoparticle is optimally positioned within the nanojet, the backscattering of the microsphere can greatly increase: for example, by 3:1 (200%) for the 50 nm gold nanoparticle. The increased backscattering is strongly dependent upon the illumination wavelength and the numerical aperture of the imaging system, and occurs for nonresonant illuminations of the isolated microsphere. Low objective numerical apertures of approximately 0.075 yield the maximum observed increases in backscattering. The measured data agree well with numerical calculations incorporating Mie-based theory and Fourier optics.
authors.affiliation: Department of Biomedical Engineering, Northwestern University, McCormick School of Engineering, 2145 Sheridan Road, Evanston, Illinois 60208, USA. seungmoo-yang@northwestern.edu
authors.forename: Seungmoo
authors.initials: S
authors.lastname: Yang
authors.forename: Allen
authors.initials: A
authors.lastname: Taflove
authors.forename: Vadim
authors.initials: V
authors.lastname: Backman
mesh_terms: D004129:Dimethylpolysiloxanes / Q000737:chemistry*; D004867:Equipment Design; D006046:Gold / Q000737:chemistry*; D008027:Light; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000737:chemistry*; D008863:Microspheres; D055095:Optics and Photonics / Q000379:methods*; D017785:Photons; D012542:Scattering, Radiation; D014025:Titanium / Q000737:chemistry
chemical_list: D004129:Dimethylpolysiloxanes; C009495:titanium dioxide; C013830:baysilon; D006046:Gold; D014025:Titanium