Variation of Trapping Strength with Size and Number of Particles in a Single Trap

Jitendra Bhatt, Sachin Bhatt, Shaival Buch, Ravindra Pratap Singh, Saiyed Nisar Ali Jaaffrey

Optical tweezers use the radiation pressure to trap and manipulate the microscopic particles. Using various algorithms multiple traps are being formed which can trap a number of particles simultaneously. In contrast to multiple traps, many particles can be trapped at a single trap position. It is known that when two or more particles are trapped in a single trap they align themselves in axial direction and it appears as if only one particle is trapped. We present a study of the dependence of the optical trapping force on the number of particles in a single trap using equipartition method; the study was carried out for particles of different sizes. The trapping force was first found to increase then decrease with number of particles in trap for all particle sizes. We feel that our studies will be useful in applications of optical tweezers involving trapping of multiple particles in a single trap.
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