300 nm and 60 nm luminescent cerium-doped YAG particles were stably optically trapped in the far-field. Their residual Brownian motion was used to study the optical tweezers properties. The trapping potential was harmonic in the transverse direction. In the axial direction, the interference pattern of the counter-propagative waves was revealed by the observation of several metastable traps. Normalized transverse stiffness values of 35 and 2 pN μm−1 W−1 for 300 nm and 60 nm YAG:Ce3+ particles were measured, respectively with 3 μm tip-to-tip distance, in qualitative agreement with numerical simulations. Finally, we estimated that this optical tweezer efficiently traps particles down to 25 nm size. This point is of great interest in various applications, e.g. tag tracking within biological cells.
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| Transverse position distribution of a 300 nm YAG:Ce3+ trapped particle for several fiber tip-to-tip distances. Inset: fluorescence microscopy image of a trapped 300 nm particle. | Axial position distribution for orthogonal (blue) and parallel (red) polarizations. Bold lines are best Gaussian fits. The thin red line is a guide to the eye for peak position visualization. |
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| Normalized transverse trapping stiffness for 300 nm YAG particles as a function of fiber tip-to-tip distances. Inset: axial stiffness. | Normalized transverse trapping stiffness of a 60 nm YAG particle as a function of fiber tip-to-tip distances. Inset: fluorescence microscopy image of a trapped 60 nm YAG particle. |
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