Fast digital hologram generation and adaptive force measurement in liquid-crystal-display-based holographic tweezers

Author(s): Marcus Reicherter, Susanne Zwick, Tobias Haist, Christian Kohler, Hans Tiziani, and Wolfgang Osten

Abstract:

“Computer-generated holograms in conjunction with spatial light modulators (SLMs) offer a way to dynamically generate holograms that are adapted to specific tasks. To use the full dynamic capability of the SLM, the hologram computation should be very fast. We present a method that uses the highly parallel architecture of a consumer graphics board to compute analytical holograms in video real time. A precice characterization of the SLM (Holoeye LC-R-2500) and the adaption of its settings to our near-infrared application is necessary to guarantee an efficient hologram reconstruction. The benefits of a fast computation of adapted holograms and the application of an efficient SLM are demonstrated by measuring the trapping forces of holographic tweezers.”

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Publication: Applied Optics
Issue/Year: Applied Optics, Vol. 45, Issue 5, pp. 888-896, 2006
DOI: 10.1364/AO.45.000888

Interactive approach to optical tweezers control

Author(s): Jonathan Leach, Kurt Wulff, Gavin Sinclair, Pamela Jordan, Johannes Courtial, Laura Thomson, Graham Gibson, Kayode Karunwi, Jon Cooper, Zsolt John Laczik, and Miles Padgett

Abstract:

“We have developed software with an interactive user interface that can be used to generate phase holograms for use with spatial light modulators. The program utilizes different hologram design techniques, allowing the user to select an appropriate algorithm. The program can be used to generate multiple beams and can be used for beam steering. We see a major application of the program to be in optical tweezers to control the position, number, and type of optical traps.”

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Publication: Applied Optics
Issue/Year: Applied Optics, Vol. 45, Issue 5, pp. 897-903, 2006
DOI: 10.1364/AO.45.000897

Raman imaging of floating cells

Author(s): Caitriona Creely, Giovanni Volpe, Gajendra Singh, Marta Soler, and Dmitri Petrov

Abstract:

“Raman imaging can yield spatially resolved biochemical information from living cells. To date there have been no Raman images published of cells in suspension because of the problem of immobilizing them suitably to acquire space-resolved spectra. In this paper in order to overcome this problem the use of holographic optical tweezers is proposed and implemented, and data is shown for spatially resolved Raman spectroscopy of a live cell in suspension.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 13, Issue 16, pp. 6105-6110, 2005
DOI: 10.1364/OPEX.13.006105

3D interferometric optical tweezers using a single spatial light modulator

Author(s): Ethan Schonbrun, Rafael Piestun, Pamela Jordan, Jon Cooper, Kurt Wulff, Johannes Courtial, and Miles Padgett

Abstract:

“Hexagonal arrays of micron sized silica beads have been trapped in three-dimensions within an optical lattice formed by the interference of multiple plane-waves. The optical lattice design with sharply peaked intensity gradients produces a stronger trapping force than the traditionally sinusoidal intensity distributions of other interferometric systems. The plane waves were generated using a single, phase-only, spatial light modulator (SLM), sited near a Talbot image plane of the traps. Compared to conventional optical tweezers, where the traps are formed in the Fourier-plane of the SLM, this approach may offer an advantage in the creation of large periodic array structures. This method of pattern formation may also be applicable to trapping arrays of atoms.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 13, Issue 10, pp. 3777-3786, 2006
DOI: 10.1364/OPEX.13.003777

Experimental demonstration of holographic three-dimensional light shaping using a Gerchberg–Saxton algorithm

Author(s): Graeme Whyte and Johannes Courtial

Abstract:

“We use a three-dimensional Gerchberg–Saxton algorithm (Shabtay (2003) Opt. Commun. 226 33) to calculate the Fourier-space representation of physically realizable light beams with arbitrarily shaped three-dimensional intensity distributions. From this representation we extract a phase-hologram pattern that allows us to create such light beams experimentally. We show several examples of experimentally shaped light beams.”

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Publication: New Journal of Physics
Issue/Year: New J. Phys. 7 117, 2005
DOI: 10.1088/1367-2630/7/1/117

Assembly of 3-dimensional structures using programmable holographic optical tweezers

Author(s): Gavin Sinclair, Pamela Jordan, Johannes Courtial, Miles Padgett, Jon Cooper, and Zsolt Laczik

Abstract:

“The micromanipulation of objects into 3-dimensional geometries within holographic optical tweezers is carried out using modified Gerchberg-Saxton (GS) and direct binary search (DBS) algorithms to produce the hologram designs. The algorithms calculate sequences of phase holograms, which are implemented using a spatial light modulator, to reconfigure the geometries of optical traps in many planes simultaneously. The GS algorithm is able to calculate holograms quickly from the initial, intermediate and final trap positions. In contrast, the DBS algorithm is slower and therefore used to pre-calculate the holograms, which are then displayed in sequence. Assembly of objects in a variety of 3-D configurations is semi-automated, once the traps in their initial positions are loaded.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 12, Issue 22, pp. 5475-5480, 2004
DOI: 10.1364/OPEX.12.005475

Size selective trapping with optical ”cogwheel” tweezers

Author(s): Alexander Jesacher, Severin Fürhapter, Stefan Bernet, and Monika Ritsch-Marte

Abstract:

“We experimentally investigate the size-selective trapping behavior of Laguerre-Gaussian beams (”doughnut-beams”) and ”cogwheel”-shaped beams which are collinear superpositions of two doughnut beams of equal opposite helical index. Experimentally they are created by diffraction of a Gaussian laser beam at a high resolution refractive spatial light modulator (SLM). In the focus of an optical microscope such a beam looks similar to a ”cogwheel”, i.e. the light intensity is periodically modulated around the circumference of a sphere with a precisely adjustable diameter. In an optical tweezers setup these modes can be used to trap particles or cells, provided their sizes exceed the ring diameter by a fixed amount. This promises a convenient method of constructing an optical tweezers system in microscopy which acts as a passive sorter for particles of differing sizes.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 12, Issue 17, pp. 4129-4135, 2004
DOI: 10.1364/OPEX.12.004129

Observation of the vortex structure of a non-integer vortex beam

Author(s): Jonathan Leach, Eric Yao and Miles J Padgett

Abstract:

“An optical beam with an eilΦ phase structure carries an orbital angular momentum of lħ per photon. For integer l values, the phase fronts of such beams form perfect helices with a single screw-phase dislocation, or vortex, on the beam axis. For non-integer l values, Berry (2004 J. Opt. A: Pure Appl. Opt. 6 259) predicts a complex-phase structure comprising many vortices at differing positions within the beam cross-section. Using a spatial light modulator we produce eilΦ beams with varying l. We examine the phase structure of such beams after propagation through an interference-based phase-measurement technique. As predicted, we observe that for half-integer l values, a line of alternating charge vortices is formed near the radial dislocation. ”

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Publication:New Journal of Physics
Issue/Year: New J. Phys. 6 (2004) 71,
DOI: 10.1088/1367-2630/6/1/071

Multiple Optical Trapping by Means of Diffractive Optical Elements

Author(s): Dan Cojoc, Valentina Emiliani, Enrico Ferrari, Radu Malureanu, Stefano Cabrini, Remo Zaccaria Proiettiand Enzo Di Fabrizio

Abstract:

“In this paper we report multiple optical trapping of microscopic dielectric particles using diffractive optical elements implemented on twisted nematic liquid crystal spatial light modulators. The particles are trapped in arrays disposed in plane or in volume and can be moved independently in x-y-z by changing the configuration of the diffractive optical element. We show also multiple trapping using Laguerre-Gaussian and Gaussian beams simultaneously. The orbital angular momentum of the Laguerre-Gaussian beam is transferred to the particle, making it to move on a circular trajectory defined by the intensity pattern specific to this beam. We use sample cells built with two microscope slides separated by 120 µm with a sticky tape. The space between the two slides is filled with 2 µm diameter silica spheres diluted in water (concentration 0.026% wt). We show that optical trapping is also possible in a small glass capillary with a diameter of 100 µm. ”

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Publication: Japanese Journal of Applied Physics
Issue/Year: Jpn. J. Appl. Phys. 43 (2004) pp. 3910-3915
DOI: 10.1143/JJAP.43.3910

Diffractive optical tweezers in the Fresnel regime

Author(s): Alexander Jesacher, Severin Fürhapter, Stefan Bernet, and Monika Ritsch-Marte

Abstract:

“We demonstrate a flexible setup for holographic steering of laser tweezers in microscopy using a high resolution spatial light modulator (SLM). In contrast to other methods, hologram read-out is done in the off-axis Fresnel regime rather than in the typically used on-axis Fourier regime. The diffractive structure is calculated as a Fresnel hologram, such that after reflection at the SLM only the desired first diffraction order is guided to the input of an optical microscope, where it generates a tailored optical tweezers field. We demonstrate some advantageous features of this setup, i.e. undesired diffraction orders are suppressed, the optical traps can be easily steered in real-time by just “mouse-dragging” a hologram window at the SLM display, and a number of independently steerable optical traps can be generated simultaneously in a three-dimensional arrangement by displaying a corresponding number of adjacent hologram windows at the SLM screen.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 12, Issue 10, pp. 2243-2250, 2004
DOI: 10.1364/OPEX.12.002243
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