An active coronagraph using a liquid crystal array for exoplanet imaging: principle and testing

May, 2012

Author(s): Xi Zhang, De-Qing Ren, Yong-Tian Zhu and Jiang-Pei Dou.

Abstract:

“High-contrast imaging coronagraphs, used for the detection of exoplanets, have always adopted passive coronagraph optical components. It is therefore impossible to actively optimize the coronagraphs to achieve their best performance. To solve this problem, we propose a novel high-contrast imaging coronagraph which combines a liquid crystal array (LCA) for active pupil apodization and a deformable mirror (DM) for phase correction. The LCA we use is an amplitude-only spatial light modulator. The LCA is well calibrated and compensates for its amplitude non-uniformity and nonlinear intensity responsivity. We measured the imaging contrasts of the coronagraph system with the LCA only and without the DM deployed. Imaging contrasts of 10-4 and 10-5 can be reached at an inner working angular distance of 2.5 and 5λ/D, respectively. A simulation shows that the phase errors on the coronagraph pupil limit the contrast performance. The contrast could be further improved if a DM is deployed to correct the phase errors induced by the LCA and coronagraph optics.”

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Publication: Research in Astronomy and Astrophysics, (subscription required)

Issue/Year/DOI: Res. Astron. Astrophys., Vol. 12, Issue 5,(2012)
doi:10.1088/1674-4527/12/5/011


Experimental generation and characterization of Devil’s vortex-lenses

February, 2012

Author(s): A. Calatayud, J. A. Rodrigo, L. Remón, W. D. Furlan, G. Cristóbal und J. A. Monsoriu

Abstract:

“We propose the first experimental approach for both generation and characterization of high quality Devil’s vortex-lenses. These new type of lenses, able to produce a sequence of optical vortices, are addressed onto a programmable spatial light modulator (SLM) operating in phase-only modulation. The static aberrations arising by the lack of flatness of the SLM display are characterized and mostly compensated by using a Shack–Hartmann wavefront sensor. The analysis of the residual aberrations and their effect on the vortex-lens performance are studied. ”

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Publication: Applied Physics B: Lasers and Optics, (subscription required)

Issue/Year/DOI: Applied Physics B, Volume 106, Number 4 (2012), 915-919,
doi:10.1007/s00340-012-4913-0


Binary-Phase Spatial Light Filters for Mode-Selective Excitation of Multimode Fibers

July, 2011

Author(s): Stepniak, G.; Maksymiuk, L.; Siuzdak, J.;

Abstract:

“In this paper, spatial light modulation is proposed to increase the transmission capacity of graded-index multimode fibers. In the method, selected linearly polarized eigenmodes of the fiber are excited using simple binary-phase spatial filters. Numerical results indicate that the selectivity of the method is very high, also for fibers with perturbed profiles. The excess attenuation of the method is very low. In the experiment, a threefold increase of fiber bandwidth for several filters is obtained.”

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Publication: Journal of Lightwave Technology, (subscription required)

Issue/Year/DOI: Journal of Lightwave Technology, Volume: 29 Issue: 13, P.1980 – 1987 (2011)
doi:10.1109/JLT.2011.2155621


Could SAFE concept be applied for designing a new synthetic aperture telescope?

March, 2011

Author(s): Barak Katz and Joseph Rosen

Abstract:

“Synthetic aperture with Fresnel elements (SAFE) is an incoherent holographic imaging system in which the complete hologram is a mosaic of several holograms captured from different points of view. In this paper we investigate a new scheme of SAFE which may be used as a basis for designing a new type of synthetic aperture telescopes. Laboratory in-door experiments may provide the proof of concept for such a new design.”

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Publication: Optics Express, (free download)

Issue/Year/DOI: Optics Express, Vol. 19, Issue 6, pp. 4924-4936 (2011)
doi:10.1364/OE.19.004924


What spatial light modulators can do for optical microscopy

January, 2011

Author(s): C. Maurer, A. Jesacher, S. Bernet, M. Ritsch-Marte.

Abstract:

“With the availability of high-resolution miniature spatial light modulators (SLMs) new methods in optical microscopy have become feasible. The SLMs discussed in this review consist of miniature liquid crystal displays with micron-sized pixels that can modulate the phase and/or amplitude of an optical wavefront. In microscopy they can be used to control and shape the sample illumination, or they can act as spatial Fourier filters in the imaging path. Some of these applications are reviewed in this article. One of them, called spiral phase contrast, generates isotropic edge enhancement of thin phase samples or spiral-shaped interference fringes for thicker phase samples, which can be used to reconstruct the phase topography from a single on-axis interferogram. If SLMs are used for both illumination control and spatial Fourier filtering, this combination for instance allows for the generalization of the Zernike phase contrast principle. The new SLM-based approach improves the effective resolution and avoids some shortcomings and artifacts of the traditional method. The main advantage of SLMs in microscopy is their flexibility, as one can realize various operation modes in the same setup, without the need for changing any hardware components, simply by electronically switching the phase pattern displayed on the SLMs.”

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Publication: Laser & Photonics Reviews, (subscription required)

Issue/Year/DOI: Laser & Photonics Reviews, Volume 5, Issue 1, pages 81–101, January 2011
DOI: 10.1002/lpor.200900047


Generating Superpositions of Higher Order Bessel Beams

October, 2009

Author(s): Ruslan Vasilyeu, Angela Dudley, N. Khilo, and Andrew Forbes

Abstract:

“An experimental setup to generate a superposition of higher-order Bessel beams by means of a spatial light modulator and ring aperture is presented. The experimentally produced fields are in good agreement with those calculated theoretically.”

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Publication: Conference Paper: Frontiers in Optics (FiO) Oct 11, 2009, (subscription required)


Superhydrophobic surface structures in thermoplastic polymers by interference lithography and thermal imprinting

September, 2009

Author(s): Christian W.J. Berendsen, Marek Škereň, David Najdek and František Cerný

Abstract:

“We present a method to produce superhydrophobic surfaces in thermoplastic polymer substrates. The method involves the creation of a nickel stamp using a customized laser interference lithography technique and electroplating processes. This stamp is used to emboss sub-micrometer periodic structures into the thermoplastic. The modified surface is coated with a hydrophobic plasma-polymerized hexafluoropropene layer. Surfaces with different periodicity and relief depth were created. On the surface with the highest aspect ratio, advancing water contact angles of 167° were measured with a water contact angle hysteresis of below 5°.”

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Publication: Applied Surface Science – ScienceDirect.com (subscription required)

Issue/Year/DOI: Applied Surface Science, Volume 255, Issue 23, 15 September 2009, Pages 9305-9310
doi:10.1016/j.apsusc.2009.07.001


Spatial amplitude and phase modulation using commercial twisted nematic LCDs

April, 2008

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, (subscription required)

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


Simulating atmospheric turbulence using a phase-only spatial light modulator

March, 2008

Author(s): Burger L.; Litvin I.A.; Forbes A.

Abstract:

“Demonstration of the effect of atmospheric turbulence on the propagation of laser beams is traditionally a difficult task. This is due to the complexities of long-distance measurements and the scarcity of suitable laser wavelengths in atmospheric transmission windows. We demonstrate the simulation of atmospheric turbulence in the laboratory using a phase-only spatial light modulator. We illustrate the advantages of this approach, as well as some of the limitations, when using spatial light modulators for this application. We show experimental results demonstrating these limitations, and discuss the impact they have on the simulation of various turbulence strengths.”

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Publication: South African Journal of Science, (free download)

Issue/Year/DOI: S. Afr. j. sci. vol.104 no.3-4 Pretoria Mar./Apr. 2008
Print version ISSN 0038-2353


Demixing light paths inside disordered metamaterials

January, 2008

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, (free download)

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