Schematic diagram of the optical tweezers setup combining a pair of GMM and a SLM. (Abbreviations are defined in the main text.)
The rotation angle of the GMM results in a tilt at the back aperture of the objective. It is constrained by the geometry of the setup. Note that only one of the mirrors of the GMM is shown for clarity.
Interferometers used for determining the intensity and phase as a function of different incidence angles . (a) , (b) , and (c) . For the intensity measurements, the beam directed toward the mirror M is covered and the camera used as a power meter. (Abbreviations are defined in the main text.)
Output intensity as a function of phase shift introduced by the SLM for an incidence angle and input and output polarizations and , respectively.
Ratio between minimum and maximum intensities (Fig. 4) as a function of input, , and output, , polarizations for different incident angles , 4°, 22.5°, and 45° (top to bottom). Plateau regions are observed at and (60, 100).
Actual phase shift as a function of for an incident angle and input and output polarizations and , respectively.
Maximum range of the actual phase shift as a function of input, , and output, , polarizations for different incident angles and 45° (top and bottom). The cross-hatched areas represent configurations where the intensity of one of the fringe signals was too small to be measured, and therefore could not be determined.
Voltage sent to galvanometer and particle position together with fits as a function of time . Polystyrene sulfonate particles with a radius in water at a distance to the coverslip of about were subjected to an oscillatory optical tweezer with a laser power of 11.1 mW at a temperature of . We determined a time lag between particle and trap position of giving a trap stiffness .
Top: two-dimensional probability distribution of particle positions with within the trap. Contours of the data and fit at 5%, 20%, 40%, 60%, 80%, and 99% of maximum (outside to center) are shown. Bottom: azimuthally averaged probability distribution together with a Gaussian fit with variance , indicating a trap stiffness . The inset shows the same data and fit in a log-square representation, and the vertical line shows that as used above is within the harmonic regime (see text for details). The same sample and experimental conditions were used as in Fig. 8.
Image of six polystyrene sulfonate particles with radius , three trapped between the objective and the focal plane (e.g., top left) and three at the other side of the focal plane (e.g., top right).
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