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Reshaping of a Gaussian laser beam into a uniform or other intensity distribution is required for various applications. The laser beam shaping system with a radial birefringent filter is presented in this paper. With such a system the Gaussian beams can be transformed into uniform or annular beams. The theory and simulation of the proposed systems are described in detail. The primary advantage of such a system is that the out beam profile can be tunable with the rotation of the radial birefringent element. [ABSTRACT FROM AUTHOR]

The spinning of asymmetric objects trapped within optical tweezers that have a rotating rectangular aperture inserted into the trapping laser beam is characterized. The measured maximum rotation rates of various asymmetric micron-sized objects are in agreement with a linear dependence on laser power. Maximum rotation rates of up to 0.2 Hz per mW of laser power suggest that rotation rates in the region of 10-20 Hz should be readily achievable in commercially available tweezers that have been modified by the inclusion of a rotating rectangular aperture. In addition, the possibility to alter the orientation of the aperture allows convenient control over the orientation of tweezed objects. [ABSTRACT FROM AUTHOR]