Abstract

We have investigated the trapping force on low and high refractive index nano-particles using a highly focused Laguerre–Gaussian beam. An analytical expression for the gradient force has been derived in closed form. It was clearly found that the increase of the beam mode $p$ causes a substantial increase in the number of trapping zones, which frequently increases the number of particles to be captured simultaneously. Also, the decrease of $p$ values would increase the trap area, which consequently leads to simultaneous trapping of multiple particles in the same area. The change of $p$, $l$, $\Delta n$, and ${z_1}$ values has a direct influence on the gradient forces. The smaller values of scattering and thermal forces relative to the gradient force values represent essential conditions for the stability of the trapping performance.

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