Suppression of undesired diffraction orders of binary phase holograms

Author(s): Christian Maurer, Andreas Schwaighofer, Alexander Jesacher, Stefan Bernet, Monika Ritsch-Marte

Abstract:

“A method to remove undesired diffraction orders of computer-generated binary phase holograms is demonstrated. Normally, the reconstruction of binary Fourier holograms, made from just two phase levels, results in an undesired inverted image from the minus first diffraction order, which is superposed with the desired one. This can be avoided by reconstructing the hologram with a diffuse light field with a pseudorandom, but known, phase distribution, which is taken into account for the hologram computation. As a consequence, only the desired image is reconstructed, whereas all residual light is dispersed, propagating as a diffuse background wave. The method may be advantageous to employ ferroelectric spatial light modulators as holographic display devices, which can display only binary phase holograms, but which have the advantage of fast switching rates.”

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Publication: Applied Optics
Issue/Year: Applied Optics, Vol. 47, Issue 22, pp. 3994-3998 (2008)
DOI: 10.1364/AO.47.003994

Power amplification of a phased array steered laser beam

Author(s): C.A. SchäferCorresponding, O. Matoba, N. Kaya

Abstract:

“Steering a laser beam by an optical phased array provides non-mechanical beam steering, high angular resolution with large apertures. It is therefore considered in several applications such as laser communication and power transmission links between moving objects. However, in many devices the incident power density is limited and the fill factor leads to a high loss of light. These two drawbacks can be overcome by an amplification of the steered beam.

In this paper, we study amplification by a two wave mixing process. The steered beam gets amplified by energy transfer from a pump beam inside a nonlinear medium. By building a telescope setup, the medium can be placed at different positions leading to different characteristics of the amplification process.

We examine amplification in the image and Fourier plane. Then we also propose the Fresnel region as a compromise between the two extremes for the place of the amplification process.”

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Publication: Acta Astronautica
Issue/Year: Acta Astronautica, Volume 63, Issues 1-4, July-August 2008, Pages 334-341
DOI: 10.1016/j.actaastro.2007.12.052

Holographic Reconstructions Using Phase-Only Spatial Light Modulators

Author(s): Fahri Yaras, Metodi Kovachev, Rossitza Ilieva, Mostafa Agour, Levent Onural

Abstract:

“Phase-only spatial light modulators are used for reconstructions from inline phase holograms that are calculated by Gerchberg-Saxton iterative algorithm. Although iterative procedures are slow in computing holograms, we obtained sufficient results with a rather low number of iterations. We have shown that reconstruction of 2D objects whose sizes are larger than SLM size is possible. Not only single plane 2D objects but also several objects in different depths are reconstructed using phase holograms by superposing their complex diffraction patterns. Results of both numerical and optical reconstructions from phase holograms are satisfactory.”

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Publication:3DTV Conference: The True Vision – Capture, Transmission and Display of 3D Video
Issue/Year: 3DTV Conference: The True Vision – Capture, Transmission and Display of 3D Video, 2008
DOI: 10.1109/3DTV.2008.4569826

Femtosecond laser ablation inductively coupled plasma mass spectrometry: Fundamentals and capabilities for depth profiling analysis

Author(s): Jorge Pisonero, Detlef Günther

Abstract:

“Laser ablation coupled to inductively coupled plasma mass spectrometry has become a versatile and powerful analytical method for direct solid analysis. The applicability has been demonstrated on a wide variety of samples, where major, minor, and trace element concentrations or isotope ratio determinations have been of interest. The pros and cons of UV-nsec laser ablation have been studied in detail, and indicate that aerosol generation, aerosol transport, and aerosol excitation–ionization within the ICP contribute to fractionation effects, which prevent this method from a more universal application to all matrices and all elements. Recent progresses in IR-fs and UV-fs laser ablation coupled to ICP-MS have been reported, which increase the inter-matrix and multi-element quantification capabilities of this method. These fundamental improvements in LA-ICP-MS are of significant importance for entering new applications in material science and related research fields. In particular, because coatings (conducting and non-conducting) consist of single or multilayers of various elemental composition and of different thickness (nm–mm range), significant progress in the field of depth profiling with fs-laser ablation can be expected. Therefore, in-depth profile analysis of polymers, semiconductors, and metal sample investigations, using ultra-fast laser ablation for sampling and the currently achievable figures of merit, are discussed. In this review manuscript, the enhanced capabilities of fs-LA-ICP-MS for direct solid sampling are highlighted, and it is discussed about current methods used for quantitative analysis and depth profiling, the ablation process of UV-ns and UV-fs, the influence of the laser beam profile, aerosol structure and transport efficiency, as well as the influence of the ICP-MS (e.g., vaporization and ionization efficiency in the plasma, and type of mass analyzer).”

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Publication: Mass Spectrometry Reviews
Issue/Year: Mass Spectrometry Reviews, 2008, Volume 27, Issue 6, pages 609–623,
DOI: 10.1002/mas.20180

Structured illumination in total internal reflection fluorescence microscopy using a spatial light modulator

Author(s): Reto Fiolka, Markus Beck, and Andreas Stemmer

Abstract:

“In wide-field fluorescence microscopy, illuminating the specimen with evanescent standing waves increases lateral resolution more than twofold. We report a versatile setup for standing-wave illumination in total internal reflection fluorescence microscopy. An adjustable diffraction grating written on a phase-only spatial light modulator controls the illumination field. Selecting appropriate diffraction orders and displaying a sheared (tilted) diffraction grating allows one to tune the penetration depth in very fine steps. The setup achieves 91 nm lateral resolution for green emission.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 33, Issue 14, pp. 1629-1631
DOI: 10.1364/OL.33.001629

Phase dynamics of continuous topological upconversion in vortex beams

Author(s): Carlos López-Mariscal, Daniel Burnham, Daniel Rudd, David McGloin, and Julio C. Gutiérrez-Vega

Abstract:

“The vortex emergence process as an integer order Bessel field progresses continuously onto the contiguous higher order Bessel field is studied in detail. We assess the progressive migration of phase singularities and explain the predicted increase in fractional orbital angular momentum content of the beam in terms of this gradual process.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 15, pp. 11411-11422, (2008)
DOI: 10.1364/OE.16.011411

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

An efficient method for the creation of tunable optical line traps via control of gradient and scattering forces

Author(s): Gregory T. Tietjen, Yupeng Kong, and Raghuveer Parthasarathy

Abstract:

“Interparticle interaction energies and other useful physical characteristics can be extracted from the statistical properties of the motion of particles confined by an optical line trap. In practice, however, the potential energy landscape, U(x), imposed by the line provides an extra, and in general unknown, influence on particle dynamics. We describe a new class of line traps in which both the optical gradient and scattering forces acting on a trapped particle are designed to be linear functions of the line coordinate and in which their magnitude can be counterbalanced to yield a flat U(x). These traps are formed using approximate solutions to general relations concerning non-conservative optical forces that have been the subject of recent investigations [Y. Roichman, B. Sun, Y. Roichman, J. Amato-Grill, and D. G. Grier, Phys. Rev. Lett. 100, 013602-4 (2008).]. We implement the lines using holographic optical trapping and measure the forces acting on silica microspheres, demonstrating the tunability of the confining potential energy landscape. Furthermore, we show that our approach efficiently directs available laser power to the trap, in contrast to other methods.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 14, pp. 10341-10348 (2008)
DOI: 10.1364/OE.16.010341

A Projection System for Real World Three-Dimensional Objects Using Spatial Light Modulators

Author(s): Gopinathan, U. Monaghan, D.S. Hennelly, B.M. McElhinney, C.P. Kelly, D.P. McDonald, J.B. Naughton, T.J. Sheridan, J.T.

Abstract:

“We discuss a projection system for real world three-dimensional objects using spatial light modulators (SLM). An algorithm to encode the digital holograms of real world objects on to an SLM is presented. We present results from experiments to project holograms of real world holograms using a nematic liquid crystal SLM. We discuss the case when the pixel sizes of the charge-coupled device (CCD) and SLM used for recording the hologram and projection are different.”

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Publication: Journal of Display Technology
Issue/Year: Journal of Display Technology, Volume 4, Issue 2, June 2008, Pages 254-261
DOI: 10.1109/JDT.2007.913943
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