title: High-numerical-aperture microlensed tip on an air-clad optical fiber.
abstract: We show that a hemispherically shaped tip on an air-clad optical fiber simultaneously works as a high-numerical-aperture lens and efficiently collects photons from an emitter placed near the beam waist into the fundamental guided mode. Numerical simulations show that the coupling efficiency reaches about 25%. We have constructed a confocal microscope with such a lensed fiber. The measurements are in good agreement with the numerical simulation. The monolithic structure with a high-photon-collection efficiency will provide a flexible substitute for a conventional lens system in various experiments such as single-atom trapping with a tightly focused optical trap.
authors.forename: Shinya
authors.initials: S
authors.lastname: Kato
authors.forename: Sho
authors.initials: S
authors.lastname: Chonan
authors.forename: Takao
authors.initials: T
authors.lastname: Aoki
mesh_terms: D000388:Air; D007909:Lenses; D055616:Microtechnology / Q000295:instrumentation*; D055100:Optical Fibers; D017785:Photons