Thousands of traps in counter-propagating Bessel beams
The uniques preoperties of the Bessel beam can be also efficiently used in counter-propagating and interfering Bessel beams. Since the single real beam Bessel beam has negligible intensity gradients along the propagatin axis it can not be used to trap an objects. But two interfering and counter-propagatin Bessel beams create a standing wave. On the contrast to the Gaussian beam where each trap has different properties than its neighboring trap (see figure), the standing Bessel beam creates an array of very similar optical traps. Moreover the traps are narrow lateraly and also axially and an array of them long millimetres can be obtained. Therefore thousands of optical trapps in 3D can be generated and thousands of objects can be trapped there.
An example of an intensity profile of a standing wave created by two counter-propagating Bessel beams.
The neighboring trapps are very simillar to each other.
Experimentally we used two identical counter-propagating Bessel beams at the wavelength of 532 nm with carefully designed paths so that each Bessel beam existed over a distance 1 mm and its diameter of the high intensity core was only 2 micrm.
Using this setup we suceeded in confinement about thousands of polystyrene beads of radius 175 nn in 1 mm long array.
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Last modification: 30 Mar 2007