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

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

A new method for three-dimensional tracking using a liquid crystal on silicon (LCoS)

Author(s): Matías A Goldin, Guadalupe Díaz Costanzo, Oscar E Martínez, Claudio Iemmi, Silvia Ledesma

Abstract:

“Imaging of samples by different microscopy techniques has produced a relevant impact in the development of new diagnosis techniques in biology, medicine, and material science. In many biological applications, where the sample changes or moves during the observation, a dynamical focusing of the microscope is needed. To this end it is necessary to localize the sample previously to the refocusing process. We introduce here an optical system that can perform three-dimensional (3D) tracking without mechanical displacements. The system is based on the use of a high resolution liquid crystal on silicon (LCoS) device working as a phase mostly wavefront modulator. The additional advantage of this system is performing the motion of the spot at video rate. By using elliptical polarization we have experimentally found a configuration where the phase modulation is 2π and the intensity modulation has a variation less than 25%. For this configuration we show how the spot can be moved through the focus plane by means of linear phases, or displaced out of this plane by using a quadratic phase.”

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Publication: Journal of Optics A
Issue/Year: J. Opt. A: Pure Appl. Opt., Volume 10, Number 10, pp. 104001
DOI: 10.1088/1464-4258/10/10/104001

Prediction of phase-mostly modulation for holographic optical tweezers

Author(s): J. Andilla , E. Martín-Badosa, S. Vallmitjana

Abstract:

“We characterize a reflective Holoeye LC-R 2500 spatial light modulator with a technique in which Jones matrices describing its polarization capabilities are obtained and then used for any arbitrary configuration. We apply this method to predict a phase-mostly modulation response with minimum amplitude contrast and a phase modulation range close to 2π rad. This allows us to generate multiple traps in a holographic optical tweezers setup with high light efficiency and hardly any unwanted energy on the zero diffraction order.”

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Publication: Optics Communications
Issue/Year: Optics Communications, Volume 281, Issue 14, 15 July 2008, Pages 3786-3791
DOI: 10.1016/j.optcom.2008.03.067

High throughput diffractive multi-beam femtosecond laser processing using a spatial light modulator

Author(s): Zheng Kuang, Walter Perrie, Jonathan Leach, Martin Sharp, Stuart P. Edwardson, Miles Padgett, Geoff Dearden and Ken G. Watkins

Abstract:

“High throughput femtosecond laser processing is demonstrated by creating multiple beams using a spatial light modulator (SLM). The diffractive multi-beam patterns are modulated in real time by computer generated holograms (CGHs), which can be calculated by appropriate algorithms. An interactive LabVIEW program is adopted to generate the relevant CGHs. Optical efficiency at this stage is shown to be ~50% into first order beams and real time processing has been carried out at 50 Hz refresh rate. Results obtained demonstrate high precision surface micro-structuring on silicon and Ti6Al4V with throughput gain >1 order of magnitude.”

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Publication: Applied Surface Science
Issue/Year: Applied Surface Science, Volume 254 – 2008 (2008)
DOI: 10.1016/j.apsusc.2008.07.091

Spatial amplitude and phase modulation using commercial twisted nematic LCDs

Author(s): E. G. van Putten, I. M. Vellekoop, and A. P. Mosk

Abstract:

“We present a method for full spatial phase and amplitude control of a laser beam using a twisted nematic LCD combined with a spatial filter. By spatial filtering we combine four neighboring pixels into one superpixel. At each superpixel we are able to independently modulate the phase and the amplitude of light. We experimentally demonstrate the independent phase and amplitude modulation using this novel technique. Our technique does not impose special requirements on the spatial light modulator and allows precise control of fields even with imperfect modulators.”

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Publication: Applied Optics
Issue/Year: Applied Optics, Vol. 47, Issue 12, pp. 2076-2081, 2008
DOI: 10.1364/AO.47.002076

Wavelength dependence of polarimetric and phase-shift characterization of a liquid crystal on silicon display

Author(s): A. Lizana, A. Marquez, I. Moreno, C. Iemmi, J. Campos, M.J. Yzuel

Abstract:

“We present a full characterization of a liquid-crystal-on-silicon (LCoS) display, including a polarimetric analysis based on the Mueller-Stokes formalism, and a phase shift modulation calibration. Results for different wavelengths are compared. The goal of this work is two fold. On one side, previous papers dealing with the illumination wavelength 633 nm have shown that LCoS produce a non negligible amount of depolarized light. This may have a negative impact in certain applications. Here we want to establish how this depolarization varies with the wavelength. On the other side, to use the LCoS as a spatial light modulator (SLM) we need to obtain optimal configurations enabling for phase-only or for amplitude-only modulation. Here we show how phase-only modulation is obtained, and how it evolves with the wavelength. In principle, for shorter wavelengths the phase modulation depth increases and the energy throughput may also be increased. However, these phase-only configurations may be partially degraded by the presence of depolarization at certain gray levels. Thus, the Mueller-Stokes formalism is necessary to get a full picture of the performance exhibited by the LCoS at each wavelength”

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Publication: Journal of the European Optical Society
Issue/Year: Journal of the European Optical Society, Vol 3 (2008)
DOI: 10.2971/jeos.2008.08012

Combined Mueller and Jones matrix method for the evaluation of the complex modulation in a liquid-crystal-on-silicon display

Author(s): I. Moreno, A. Lizana, J. Campos, A. Márquez, C. Iemmi, and M. J. Yzuel

Abstract:

“We apply the polar decomposition of the Mueller matrix describing a liquid-crystal-on-silicon display to identify the diattenuator, depolarizer, and retarder contributions as a function of the gray level. The retarder contribution is expressed in terms of the equivalent Jones matrix to apply previous techniques to evaluate the phase modulation. This allows searching for optimized polarization configurations for phase- or amplitude-only modulation responses. We present results for λ=633 nm showing a phase-only modulation up to 2π rad and flat intensity modulation.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 33, Issue 6, pp. 627-629, 2008
DOI: 10.1364/OL.33.000627

The very long range nature of capillary interactions in liquid films

Author(s): Di Leonardo R, Saglimbeni F, Ruocco G.

Abstract:

“Micron-sized objects confined in thin liquid films interact through forces mediated by the deformed liquid-air interface. These capillary interactions provide a powerful driving mechanism for the self-assembly of ordered structures such as photonic materials or protein crystals. We demonstrate how optical micro-manipulation allows the direct measurement of capillary interactions between mesoscopic objects. The force falls off as an inverse power law in particles separation. We derive and validate an explicit expression for this exponent whose magnitude is mainly governed by particle size. For micron-sized objects we found an exponent close to, but smaller than 1, making capillary interactions a unique example of strong and very long ranged forces in the mesoscopic world.”

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Publication: Physical Review Letters
Issue/Year: Phys. Rev. Lett., Volume 100, Issue 10, 106103 (2008)
DOI: 10.1103/PhysRevLett.100.106103
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