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.
© 1998 Optical Society of America
(170.2520) Medical optics and biotechnology : Fluorescence microscopy
(170.4520) Medical optics and biotechnology : Optical confinement and manipulation
(170.6280) Medical optics and biotechnology : Spectroscopy, fluorescence and luminescence
(190.4180) Nonlinear optics : Multiphoton processes
Zhanxiang Zhang, Gregory J. Sonek, Hong Liang, Michael W. Berns, and Bruce J. Tromberg, "Multiphoton Fluorescence Excitation in Continuous-Wave Infrared Optical Traps," Appl. Opt. 37, 2766-2773 (1998)