Fig. 1. Transverse force distributions produced by tightly focused laser pulses for the particle with self-focusing (n2=5.9×10−17  m2/W), without nonlinearity (n2=0), and with self-defocusing (n2=−5.9×10−17  m2/W) in the x-y plane (z=0), by taking NA=0.85 and a=40  nm. The magnitudes and directions of the transverse forces are illustrated by the colorbar and arrows in (a)–(i), respectively. (j)–(l) give the force profiles along the x direction shown in the above three rows.

Fig. 2. Longitudinal force distributions produced by tightly focused laser pulses for the particle with self-focusing (n2=5.9×10−17  m2/W), without nonlinearity (n2=0), and with self-defocusing (n2=−5.9×10−17  m2/W) in the x-z plane (y=0), by taking NA=0.85 and a=40  nm. The bottom row gives the force profiles along the z direction shown in the above three rows. Arrows in the figures denote the directions of the longitudinal forces.

Fig. 3. Force profiles along the x direction for y=0 and z=0. (a) Different values of n2, NA=0.85, and a=40  nm. (c) Different values of NA, n2=6×10−17  m2/W, and a=40  nm. (e) Different values of a, n2=6×10−17  m2/W, and NA=0.85. (b), (d), and (f) are the maximum force Fmax versus n2, NA, and a, respectively.

Fig. 4. Trapping potential along (a) x direction and (b) z direction with three different values of n2 (i.e., 5.9×10−17, 0, −5.9×10−17  m2/W), NA=0.85, and a=40  nm.