6. Spherical bead immersed in liquid and trapped by a focused beam In this section we present the distribution of force in and around a spherical particle of radius rs=1.0um and index ns =1.6 immersed in a liquid of index n,= 1. 3. The particle is displaced along the x-axis, its center being at(x,y, =)=(Ar, 0,0). The incident beam, obtained by focusing a n,=0.65um plane-wave through a 1.25NA immersion objective, is sourced at (x, y,=)=(0, 0, 1. 2um)and propagates in the negative --direction. The beam entering the objective's pupil may be circularly or linearly polarized. The actual point of focus can be placed at various locations along the =-axis, (,y, 2)=(0, 0, 4), inside or outside the spherical particle. The lens is designed for diffraction-limited focusing within the immersion liquid and in the absence of the spherical particle, the focused spot is free from aberrations and has a total power (i.e, integrated S: within the focal plane)of P=0.5 mW ( x Lucm] 005 1.0050 1.00.5 Fig 8. Cross-sectional plots of force-density component distributions(color contours) through the center of dielectric sphere(r,=1.0 um, n, =1.6), centered at(x, y, =)=(0.25um, 0, 0)and m: Fr, Fy F2. Left to right: xy-plane, xs-plane, y=-plane. The circularly-polarized ncident beam is focused at(x (0, 0, 0.7um)through a 1. 25NA immersion objective. #6863·$1500US Received 14 January 2005; revised 15 March 2005; accepted 15 March 2005 (C)2005OSA 4 April 2005/VoL 13, No. 7/OPTICS EXPRESS 23316. Spherical bead immersed in liquid and trapped by a focused beam In this section we present the distribution of force in and around a spherical particle of radius rs = 1.0µm and index ns = 1.6 immersed in a liquid of index no = 1.3. The particle is displaced along the x-axis, its center being at (x, y, z) = (∆x, 0, 0). The incident beam, obtained by focusing a λo = 0.65µm plane-wave through a 1.25NA immersion objective, is sourced at (x, y, z) = (0, 0, 1.2µm) and propagates in the negative z-direction. The beam entering the objective’s pupil may be circularly or linearly polarized. The actual point of focus can be placed at various locations along the z-axis, (x, y, z) = (0, 0, ∆z), inside or outside the spherical particle. The lens is designed for diffraction-limited focusing within the immersion liquid and, in the absence of the spherical particle, the focused spot is free from aberrations and has a total power (i.e., integrated Sz within the focal plane) of P = 0.5 mW. Fig. 8. Cross-sectional plots of force-density component distributions (color contours) through the center of dielectric sphere (rs = 1.0 µm, ns = 1.6), centered at (x, y, z) = (0.25µm, 0, 0) and immersed in a medium of index no = 1.3. The arrows show the projection of the force density vector in the cross-sectional plane, e.g., plots on the yz-plane show the (Fy, Fz) vector field. Top to bottom: Fx, Fy, Fz. Left to right: xy-plane, xz-plane, yz-plane. The circularly-polarized incident beam is focused at (x, y, z) = (0, 0, 0.7µm) through a 1.25NA immersion objective. (C) 2005 OSA 4 April 2005 / Vol. 13, No. 7 / OPTICS EXPRESS 2331 #6863 - $15.00 US Received 14 January 2005; revised 15 March 2005; accepted 15 March 2005