title: Photonic nanojet focusing for hollow-core photonic crystal fiber probes.
abstract: Large-pitch kagome-lattice hollow-core photonic crystal fibers (HC-PCFs) offer appealing optical properties for beam delivery and remote sensing. However, focusing their optical mode on a submicrometer spot can be challenging due to the large mode diameter and low numerical aperture of these fibers. Here, we demonstrate that a 30 μm latex microsphere directly set at the HC-PCF end-face provides an efficient means to focus the fiber mode down to a spot of 540 nm full width at half-maximum thanks to a photonic nanojet effect. The system is used for fluorescence imaging and direct laser writing on a thin absorbing layer. Potential applications include inspection of semiconductor wafers, photolithography, laser surgery, fluorescence sensing, or optical transfection.
authors.affiliation: CNRS, Aix Marseille Université, Ecole Centrale Marseille, Institut Fresnel, Marseille, France.
authors.forename: Petru
authors.initials: P
authors.lastname: Ghenuche
authors.forename: Hervé
authors.initials: H
authors.lastname: Rigneault
authors.forename: Jérôme
authors.initials: J
authors.lastname: Wenger