In this work we present the design process as well as experimental results of an optical system for trapping particles in air. For positioning applications of micro-sized objects onto a glass wafer we developed a highly efficient optical tweezer. The focus of this paper is the iterative design process where we combine classical optics design software with a ray optics based force simulation tool. Thus we can find the best compromise which matches the optical systems restrictions with stable trapping conditions. Furthermore we analyze the influence of manufacturing related tolerances and errors in the alignment process of the optical elements on the optical forces. We present the design procedure for the necessary optical elements as well as experimental results for the aligned system.
Mie theory describes the scattering of electromagnetic waves on spheroidal particles whose diameter is comparable to the wavelength of the incident radiation. We have implemented a parallel algorithm using graphics adapters to calculate perpendicular and parallel polarized scattered waves, from which other scattering parameters can be derived. This facilitates parallel propagation of monochromatic electromagnetic waves in scattering media. We have shown that a parallelization can reduce computation time rigorously.
Compared to conventional optics like singlet lenses or even microscope objectives advanced optical designs help to
develop properties specifically useful for efficient optical tweezers. We present an optical setup providing a customized
intensity distribution optimized with respect to large trapping forces. The optical design concept combines a refractive
double axicon with a reflective parabolic focusing mirror. The axicon arrangement creates an annular field distribution
and thus clears space for additional integrated observation optics in the center of the system. Finally the beam is focused
to the desired intensity distribution by a parabolic ring mirror. The compact realization of the system potentially opens
new fields of applications for optical tweezers such as in production industries and micro-nano assembly.
The performance of optical systems is typically improved by adding conventional optical components which is
automatically connected to an increasing system size and weight. Hybrid optical freeform components can help to
overcome this traditional tradeoff by designing a single complex optical surface that performs several optical functions at
once. In this article we present the synthetic design and integrated fabrication of a reflective hybrid beam shaper offering
beam deflection, transformation and splitting capabilities. The shape accuracy and surface quality of the component are
demonstrated with profilometric measurements. Experimental investigations of the optical performance verify the
suitability of the applied fabrication methods and design approach.