Three-dimensional parallel holographic micropatterning using a spatial light modulator

Author(s): Nathan J. Jenness, Kurt D. Wulff, Matthew S. Johannes, Miles J. Padgett, Daniel G. Cole, and Robert L. Clark

Abstract:

“We present a micropatterning method for the automatic transfer and arbitrary positioning of computer-generated three-dimensional structures within a substrate. The Gerchberg-Saxton algorithm and an electrically addressed spatial light modulator (SLM) are used to create and display phase holograms, respectively. A holographic approach to light manipulation enables arbitrary and efficient parallel photo-patterning. Multiple pyramidal microstructures were created simultaneously in a photosensitive adhesive. A scanning electron microscope was used to confirm successful replication of the desired microscale structures. ”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 20, pp. 15942-15948 (2008)
DOI: 10.1364/OE.16.015942

Collisions of Dark Solitons in Elongated Bose-Einstein Condensates

Author(s): S. Stellmer, C. Becker, P. Soltan-Panahi, E.-M. Richter, S. Dörscher, M. Baumert, J. Kronjäger, K. Bongs, and K. Sengstock

Abstract:

“We present experimental data showing the head-on collision of dark solitons generated in an elongated Bose-Einstein condensate. No discernable interaction can be recorded, in full agreement with the fundamental theoretical concepts of solitons as mutually transparent quasiparticles. Our soliton generation technique allows for the creation of solitons with different depths; hence, they can be distinguished and their trajectories be followed. Simulations of the 1D-Gross-Pitaevskii equation have been performed to compare the experiment with a mean-field description.”

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Publication: Physical Review Letters
Issue/Year: Phys. Rev. Lett. 101, Issue 12, 120406 (2008)
DOI: 10.1103/PhysRevLett.101.120406

Hydrodynamic interactions in two dimensions

Author(s): R. Di Leonardo, S. Keen, F. Ianni, J. Leach, M. J. Padgett and G. Ruocco

Abstract:

“We measure hydrodynamic interactions between colloidal particles confined in a thin sheet of fluid. The reduced dimensionality, compared to a bulk fluid, increases dramatically the range of couplings. Using optical tweezers we force a two body system along the eigenmodes of the mobility tensor and find that eigenmobilities change logarithmically with particle separation. At a hundred radii distance, the mobilities for rigid and relative motions differ by a factor of 2, whereas in bulk fluids, they would be practically indistinguishable. A two dimensional counterpart of Oseen hydrodynamic tensor quantitatively reproduces the observed behavior, once the relevant boundary conditions are recognized. These results highlight the importance of dimensionality for transport and interactions in colloidal systems and proteins in biological membranes.”

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Publication: Physical Review E
Issue/Year: Phys. Rev. E 78, Issue 3, 031406 (2008)
DOI: 10.1103/PhysRevE.78.031406

Universal Optimal Transmission of Light Through Disordered Materials

Author(s): I. M. Vellekoop and A. P. Mosk

Abstract:

“We experimentally demonstrate increased diffuse transmission of light through strongly scattering materials. Wave front shaping is used to selectively couple light to the open transport eigenchannels, specific solutions of Maxwell’s equations which the sample transmits fully, resulting in an increase of up to 44% in the total angle-integrated transmission compared to the case where plane waves are incident. The results for each of several hundreds of experimental runs are in excellent quantitative agreement with random matrix theory. From our measurements we conclude that with perfectly shaped wave fronts the transmission of a disordered sample tends to a universal value of 2/3, regardless of the thickness.”

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Publication: Physical Review Letters
Issue/Year: Phys. Rev. Lett., Volume 101, Issue 12, 120601 (2008)
DOI: 10.1103/PhysRevLett.101.120601

Novel approaches to the design of halftone masks for analog lithography

Author(s): Marcel Teschke and Stefan Sinzinger

Abstract:

“We report novel approaches to the design of halftone masks for analog lithography. The approaches are derived from interferometric phase contrast. In a first step we show that the interferometric phase-contrast method with detour holograms can be reduced into a single binary mask. In a second step we introduce the interferometric phase-contrast method by interference of the object wavefront with the conjugate object wavefront. This method also allows for a design of a halftone mask. To use kinoform holograms as halftone phase masks, we show in a third step the combination of the zeroth-order phase-contrast technique with the interferometric phase-contrast method.”

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Publication: Applied Optics
Issue/Year: Applied Optics, Vol. 47, Issue 26, pp. 4767-4776 (2008)
DOI: 10.1364/AO.47.004767

Hologram optimization for SLM-based reconstruction with regard to polarization effects

Author(s): C. Kohler, T. Haist, X. Schwab, and W. Osten

Abstract:

“We report on first results obtained with two modified hologram optimization algorithms. These algorithms take into account the complex modulation characteristic of the spatial light modulators employed for hologram reconstruction. To this end the Jones matrices of the modulator as well as all other components of the setup are used within a modified direct binary search and an iterative Fourier transform algorithm. Geometrical phase effects are included in the optimization. Elimination of the analyzer behind the spatial light modulator is possible by that approach and for typical setups using twisted-nematic liquid crystal modulators an enhanced overall diffraction efficiency is achieved. Possible applications are the comparative digital holography and optical tweezers. Experimental results for the reconstructions of holograms with a Holoeye LC-R 3000 modulator are presented.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 19, pp. 14853-14861 (2008)
DOI: 10.1364/OE.16.014853