Holographic microscopy and calculations in three dimensions are used to explore how properties of an optical trap, such as stiffness and trapping position, are influenced by other traps in its vicinity. The influence of individual traps is not limited to their diffraction-limited spot in the trapping plane, and creating a true 1D line trap is not straightforward. Here, we use a Mie–Debye representation, including the effect of spherical aberrations, to calculate the force fields. We compare the calculations with experiments on a single particle in a linear array of three traps. We vary the spacing between the traps and measure the particle’s trajectory using video holographic microscopy. Thus we can study the effect of nearby traps on the trapping position and trapping stiffness in 3D. We find almost quantitative agreement between theory and experiments which allows us to predict the effect of arrays of optical traps.
© 2009 Optical Society of AmericaPDF Article