Focusing coherent light through opaque strongly scattering media

Complex Photonic Systems, Faculty of Science and Technology and MESA+ Research Institute, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
Optics Letters (Impact Factor: 3.29). 09/2007; 32(16):2309-11. DOI: 10.1364/OL.32.002309
Source: PubMed


We report focusing of coherent light through opaque scattering materials by control of the incident wavefront. The multiply scattered light forms a focus with a brightness that is up to a factor of 1000 higher than the brightness of the normal diffuse transmission.

34 Reads
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    • "In scattering medium the energy of the initial beam is not lost but is instead converted into a diffuse glow of scattered light. This diffusively scattered light makes objects look blurred and thus represents a major obstacle to the imaging and focusing of light in different fields such as biomedical imaging, laser therapy, oceanology [1] [2]. "
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    ABSTRACT: It is well known that turbid medium such as fog or biological tissues causes light scatter. This phenomenon is known as major impediment for imaging and focusing of light. Thus it is important to understand the impact of the turbid medium on the light characteristics, namely intensity and phase distributions. In this work laser beam propagation through the scattering suspension of polystyrene microspheres in distilled water was investigated both theoretically and experimentally. We obtained the dependence of the wavefront aberrations on the particles concentration and shown the existence of high-order symmetric wavefront aberrations of the laser beam passed through turbid medium. The investigation showed that with the use of bimorph deformable mirror the wavefront aberrations of scattered light could be effectively corrected.
    SPIE Unconventional Imaging and Wavefront Sensing 2015; 09/2015
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    • "In 1990 Freund predicted that precise optical devices could be made using opaque media and wavefront shaping [1]. Since then this technique has been used to control: transmission through opaque materials [2], the polarization of light [3] [4], broadband spectral characteristics [5] [6] [7] [8], and the spatio-spectral properties of random lasers [9] [10] [11] [12]. It has also been used to enhance fluorescence microscopy [13] [14], achieve perfect focusing [13] [15], compress ultrashort pulses [16] [17] and enhance astronomical and biological imaging [18] [19]. "
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    ABSTRACT: The method of wavefront shaping to control optical properties of opaque media is a promising technique for authentication applications. One of the main challenges of this technique is the sensitivity of the wavefront-sample coupling to translation and/or rotation. To better understand how translation and rotation affect the wavefront- sample coupling we perform experiments in which we first optimize reflection from an opaque surface—to obtain an optimal wavefront—and then translate or rotate the surface and measure the new reflected intensity pattern. By using the correlation between the optimized and translated or rotated patterns we determine how sensitive the wavefront-sample coupling is. These experiments are performed for different spatial-light-modulator (SLM) bin sizes, beam-spot sizes, and nanoparticle concentrations. We find that all three parameters affect the different positional changes, implying that an optimization scheme can be used to maximize the stability of the wavefront-sample coupling. We also develop a model to simulate sample translation or rotation and its effect on the coupling stability, with the simulation results being qualitatively consistent with experiment.
    Physical Review A 06/2015; 91(6):063802. DOI:10.1103/PhysRevA.91.063802 · 2.81 Impact Factor
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    • "In optics, wavefront shaping by spatial light modulators (SLMs) has emerged as a powerful tool to control the speckle and thus light propagation through such complex media [7]. Different approaches have been proposed, in particular via optimisation methods [8], to focus light through [9] or into [10] a complex medium. However, a more general way to understand light propagation is to describe it via its transmission matrix (TM) [11] and, recently, we introduced a method to measure the monochromatic transmission matrix of a complex medium and to subsequently demonstrate focusing and imaging through an opaque scattering medium [12] [13]. "
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    ABSTRACT: We present a method to measure the spectrally-resolved transmission matrix of a multiply scattering medium, thus allowing for the deterministic spatiospectral control of a broadband light source by means of wavefront shaping. As a demonstration, we show how the medium can be used to selectively focus one or many spectral components of a femtosecond pulse, and how it can be turned into a controllable dispersive optical element to spatially separate different spectral components to arbitrary positions.
    Scientific Reports 05/2015; 5:10347. DOI:10.1038/srep10347 · 5.58 Impact Factor
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