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

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

Femtosecond pulse shaping in two dimensions: Towards higher complexity optical waveforms

Author(s): V. R. Supradeepa, Chen-Bin Huang, Daniel E. Leaird, Andrew M. Weiner

Abstract:

“We demonstrate a new Fourier pulse shaping apparatus capable of achieving simultaneous high resolution and broad bandwidth operation by dispersing frequency components in a two dimensional geometry through simultaneous use of a high resolution and a broad bandwidth spectral disperser. We show experimental results which demonstrate significant improvements in achievable waveform complexity (number of controllable temporal/spectral features). We also demonstrate experiments of line-by-line pulse shaping with optical frequency combs. In this regime our configuration would allow significant enhancement of the number of controllable spectral lines which may further enhance recently demonstrated massively parallel approaches to spectroscopic sensing using frequency combs.”

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Publication:Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 16, pp. 11878-11887 (2008)
DOI: 10.1364/OE.16.011878

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

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

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

Oscillations and interactions of dark and dark–bright solitons in Bose–Einstein condensates

Author(s): Christoph Becker, Simon Stellmer, Parvis Soltan-Panahi, Sören Dörscher, Mathis Baumert, Eva-Maria Richter, Jochen Kronjäger, Kai Bongs & Klaus Sengstock

Abstract:

“Solitons are among the most distinguishing fundamental excitations in a wide range of nonlinear systems such as water in narrow channels, high-speed optical communication, molecular biology and astrophysics. Stabilized by a balance between spreading and focusing, solitons are wave packets that share some exceptional generic features such as form stability and particle-like properties. Ultracold quantum gases represent very pure and well-controlled nonlinear systems, therefore offering unique possibilities to study soliton dynamics. Here, we report on the observation of long-lived dark and dark–bright solitons with lifetimes of up to several seconds as well as their dynamics in highly stable optically trapped 87Rb Bose–Einstein condensates. In particular, our detailed studies of dark and dark–bright soliton oscillations reveal the particle-like nature of these collective excitations for the first time. In addition, we discuss the collision between these two types of solitary excitation in Bose–Einstein condensates.”

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Publication: Nature Physics
Issue/Year: Nature Physics 4, 496 – 501 (2008)
DOI: 10.1038/nphys962

Spectral and temporal response of liquid-crystal-on-silicon spatial light modulators

Author(s): Martin Bock, Susanta Kumar Das, Ruediger Grunwald, Stefan Osten, Peter Staudt and Gero Stibenz

Abstract:

“Spectral and temporal phase response of selected types of liquid-crystal-on-silicon spatial light modulators were studied using femtosecond pulses, determining specific transfer functions of the devices. The phase response resulting from programed gray level distributions was detected by analyzing the diffraction characteristics and by spectral phase interferometry for direct electric-field reconstruction. The results indicate the appearance of distinct parameter ranges that enable minimum spatiotemporal distortion. Weak oscillations in the spectral phase are explained by Gires–Tournois resonances [F. Gires and P. Tournois, Acad. Sci. Paris, C. R. 258, 6112 (1964)].”

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Publication: Applied Physics Letters
Issue/Year: Appl. Phys. Lett. 92, 151105 (2008)
DOI: 10.1063/1.2909115

Demixing light paths inside disordered metamaterials

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

Abstract:

“We experimentally demonstrate the first method to focus light inside disordered photonic metamaterials. In such materials, scattering prevents light from forming a geometric focus. Instead of geometric optics, we used multi-path interference to make the scattering process itself concentrate light on a fluorescent nanoscale probe at the target position. Our method uses the fact that the disorder in a solid material is fixed in time. Therefore, even disordered light scattering is deterministic. Measurements of the probes fluorescence provided the information needed to construct a specific linear combination of hundreds of incident waves, which interfere constructively at the probe.”

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Publication:Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 1, pp. 67-80, 2008
DOI: 10.1364/OE.16.000067

Phase and amplitude pulse shaping with two-dimensional phase-only spatial light modulators

Author(s): Eugene Frumker and Yaron Silberberg

Abstract:

“We consider a programmable, phase, and amplitude femtosecond pulse shaper based on a two-dimensional (2D) reflective liquid-crystal (LC) spatial light modulator (SLM). A new zero-order pulse shaping scheme is introduced and compared to the first-order scheme, both theoretically and experimentally, using liquid crystal on silicon 2D SLM. While the spectral components of the pulse are spread across the horizontal dimension, we use the vertical direction for modulation of both spectral phases and amplitudes. It was found that while zero-order approach provided better light efficiency (67% versus 43%), the first-order scheme has superior dynamic range of amplitude modulation.”

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Publication: Journal of the Optical Society of America B
Issue/Year: JOSA B, Vol. 24, Issue 12, pp. 2940-2947
DOI: 10.1364/JOSAB.24.002940