title: Isotropic diffraction-limited focusing using a single objective lens.
abstract: Focusing a light beam through a lens produces an anisotropic spot elongated along the optical axis, because the light comes from only one side of the focal point. Using the time-reversal concept, we show that isotropic focusing can be realized by placing a mirror after the focal point and shaping the incident beam. This idea is applied to confocal microscopy and brings about a dramatic improvement of the axial resolution.
authors.affiliation: Institut Fresnel, CNRS, Aix-Marseille Université, Ecole Centrale Marseille, Campus de St Jérôme, 13013 Marseille, France.
authors.forename: Emeric
authors.initials: E
authors.lastname: Mudry
authors.forename: Eric
authors.initials: E
authors.lastname: Le Moal
authors.forename: Patrick
authors.initials: P
authors.lastname: Ferrand
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Chaumet
authors.forename: Anne
authors.initials: A
authors.lastname: Sentenac