Numerical Analysis of Optical Trapping Force Affected by Lens Misalignments

Abstract

Geometrical optics approximation is a classic method for calculating the optical trapping force on particles whose sizes are larger than the wavelength of the trapping light. In this study, the effect of the lens misalignment on optical force was analyzed in the geometrical optics regime. We used geometrical optics to analyze the influence of off-axis placement and the tilt of the lens on the trapping position and stiffness in an optical trap. Numerical calculation results showed that lens tilting has a greater impact on the optical trap force than the off-axis misalignments, and both misalignments will couple with each other and cause a shift of the equilibrium point and the asymmetry of the optical trap stiffness in different ways. Our research revealed the asymmetry in optical traps caused by lens misalignment and can provide guidance for optimize lens placement in future experiments.

Home-made optical tweezers for biomedical applications

“…For particles whose dimensions are larger than the laser's wavelength, the geometric optics model was applied to elucidate their motion [15]. This framework operates on the idea of conserving light's momentum.…”

“…This force is perpendicular to the laser beam axis, which has Gaussian intensity distributions, and it guides the entity toward the center of the laser beam. The magnitude of this force can be expressed as follows [15],…”

Simulation and Experiment of the Trapping Trajectory for Janus Particles in Linearly Polarized Optical Traps

“…The energy theory is powerful in explaining the physical principle of optical trapping, but unhelpful in describing the trapping process. On the other hand, optical force is an indispensable tool in understanding the trapping process, especially in predicting the trapping trajectory [22][23][24][25][26][27]. The geometrical optics model [28][29][30][31] and the electromagnetic scattering model [32][33][34] are two popular models used in calculating the optical force and torque for micro-sized particles.…”