111 research outputs found
Simulated holographic three-dimensional intensity shaping of evanescent-wave fields
The size of bright structures in traveling-wave light fields is limited by diffraction. This in turn limits a number of technologies, for example, optical trapping. One way to beat the diffraction limit is to use evanescent waves instead of traveling waves. Here we apply a holographic algorithm, direct search, to the shaping of complex evanescent-wave fields. We simulate three-dimensional intensity shaping of evanescent-wave fields using this approach, and we investigate some of its limitations. (c) 2008 Optical Society of America.</p
HoloTrap: Interactive hologram design for multiple dynamic optical trapping
This work presents an application that generates real-time holograms to be
displayed on a holographic optical tweezers setup; a technique that allows the
manipulation of particles in the range from micrometres to nanometres. The
software is written in Java, and uses random binary masks to generate the
holograms. It allows customization of several parameters that are dependent on
the experimental setup, such as the specific characteristics of the device
displaying the hologram, or the presence of aberrations. We evaluate the
software's performance and conclude that real-time interaction is achieved. We
give our experimental results from manipulating 5 micron-diametre microspheres
using the program.Comment: 17 pages, 6 figure
Gradual and Random Binarization of Gray Scale Holograms
A new method called gradual and random binarization (GRB) to binarize gray-scale holograms, based on an iterative algorithm, is proposed. The binarization process is performed gradually and the pixels to be binarized are chosen randomly. Errors caused by this operation are spatially diffused. A comparison with other established methods based on error diffusion, direct binary search, and iterative stepwise quantization shows that the gradual and random binarization method achieves a very good compromise between computational complexity and reconstruction quality. Optical reconstructions are presented
Simulation of superresolution holography for optical tweezers
Optical tweezers manipulate microscopic particles using foci of light beams. Their performance is therefore limited by diffraction. Using computer simulations of a model system, we investigate the application of superresolution holography for two-dimensional (2D) light shaping in optical tweezers, which can beat the diffraction limit. We use the direct-search and Gerchberg algorithms to shape the center of a light beam into one or two bright spots; we do not constrain the remainder of the beam. We demonstrate that superresolution algorithms can significantly improve the normalized stiffness of an optical trap and the minimum separation at which neighboring traps can be resolved. We also test if such algorithms can be used interactively, as is desirable in optical tweezers
Robust Digital Holography For Ultracold Atom Trapping
We have formulated and experimentally demonstrated an improved algorithm for
design of arbitrary two-dimensional holographic traps for ultracold atoms. Our
method builds on the best previously available algorithm, MRAF, and improves on
it in two ways. First, it allows for creation of holographic atom traps with a
well defined background potential. Second, we experimentally show that for
creating trapping potentials free of fringing artifacts it is important to go
beyond the Fourier approximation in modelling light propagation. To this end,
we incorporate full Helmholtz propagation into our calculations.Comment: 7 pages, 4 figure
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