A systematic study of the influence of a glass-water interface on the on-axis trapping of micrometer-sized spherical objects by optical tweezers is presented. The ways in which the escape force and the trapping position, as well as the stiffness of the trap, depend on the focusing depth, the numerical aperture, and the degree of overfilling of the objective entrance pupil are investigated. It is concluded, among other things, that objectives with the highest numerical aperture and the use of large degrees of overfilling do not always provide the optimum trapping conditions at finite depths.
© 2003 Optical Society of America
(000.1430) General : Biology and medicine
(080.2710) Geometric optics : Inhomogeneous optical media
(140.0140) Lasers and laser optics : Lasers and laser optics
(140.7010) Lasers and laser optics : Laser trapping
(180.0180) Microscopy : Microscopy
Erik Fällman and Ove Axner, "Influence of a Glass-Water Interface on the On-Axis Trapping of Micrometer-Sized Spherical Objects by Optical Tweezers," Appl. Opt. 42, 3915-3926 (2003)