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

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…

Experimental generation and characterization of Devil’s vortex-lenses

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. ”…

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

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.” Link to Publications Page Publication: Journal of Lightwave Technology, (subscription required) Issue/Year/DOI: Journal of Lightwave Technology, Volume:…

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

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.” Link to Publications Page 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

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…

Generating Superpositions of Higher Order Bessel Beams

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.” Link to Publications Page Publication: Conference Paper: Frontiers in Optics (FiO) Oct 11, 2009, (subscription required)

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

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°.”…

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.”…

Simulating atmospheric turbulence using a phase-only spatial light modulator

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…

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…