title: Multiphoton fluorescence excitation in continuous-wave infrared optical traps.
abstract: The multiphoton fluorescence excitation observed in acontinuous-wave (cw) single-beam gradient force optical trap(optical tweezers) is reported for latex beads labeled with ayellow-green fluorescent dye (BODIPY). The fluorescenceemission spectra of the yellow-green beads trapped and excited by thesame 1064-nm laser light are identical to the spectra excited by the365-nm UV light. The influence of the numerical aperture of theobjective on the slope of the log-log power-dependence has beendemonstrated for BODIPY-Oil solution under cw and pulsed-laserconditions. The possibility that three-photon excitation processoccurs is discussed within the context of a dog-bone saturationmodel. Other possibilities for the observed fluorescence excitationhave been discussed.
authors.forename: Z
authors.initials: Z
authors.lastname: Zhang
authors.forename: G J
authors.initials: GJ
authors.lastname: Sonek
authors.forename: H
authors.initials: H
authors.lastname: Liang
authors.forename: M W
authors.initials: MW
authors.lastname: Berns
authors.forename: B J
authors.initials: BJ
authors.lastname: Tromberg