title: Modulation of photonic nanojets generated by microspheres decorated with concentric rings.
abstract: A novel design of decorating microsphere surface with concentric rings to modulate the photonic nanojet (PNJ) is investigated. By introducing the concentric ring structures into the illumination side of the microspheres, a reduction of the full width at half maximum (FWHM) intensity of the PNJ by 29.1%, compared to that without the decoration, can be achieved numerically. Key design parameters, such as ring number and depth, are analyzed. Engineered microsphere with four uniformly distributed rings etched at a depth of 1.2 μm and width of 0.25 μm can generate PNJ at a FWHM of 0.485 λ (λ = 400nm). Experiments were carried out by direct observation of the PNJ with an optical microscope under 405 nm laser illumination. As a result, shrinking of PNJ beam size of 28.0% compared to the case without the rings has been achieved experimentally. Sharp FWHM of this design can be beneficial to micro/nanoscale fabrication, optical super-resolution imaging, and sensing.
authors.forename: M X
authors.initials: MX
authors.lastname: Wu
authors.forename: B J
authors.initials: BJ
authors.lastname: Huang
authors.forename: R
authors.initials: R
authors.lastname: Chen
authors.forename: Y
authors.initials: Y
authors.lastname: Yang
authors.forename: J F
authors.initials: JF
authors.lastname: Wu
authors.forename: R
authors.initials: R
authors.lastname: Ji
authors.forename: X D
authors.initials: XD
authors.lastname: Chen
authors.forename: M H
authors.initials: MH
authors.lastname: Hong