Ori Katz

French National Centre for Scientific Research, Lutetia Parisorum, Île-de-France, France

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Publications (47)141.22 Total impact

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    ABSTRACT: Diffraction-limited imaging through complex scattering media is a long sought after goal with important applications in biomedical research. In recent years, high resolution wavefront-shaping has emerged as a powerful approach to generate a sharp focus through highly scattering, visually opaque samples. However, it requires a localized feedback signal from the target point of interest, which necessitates an invasive procedure in all-optical techniques. Here, we show that by exploiting optical nonlinearities, a diffraction-limited focus can be formed inside or through a complex sample, even when the feedback signal is not localized. We prove our approach theoretically and numerically, and experimentally demonstrate it with a two-photon fluorescence signal through highly scattering biological samples. We use the formed focus to perform two-photon microscopy through highly scattering, visually opaque layers.
    05/2014;
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    ABSTRACT: We implement the photoacoustic transmission matrix approach on a two-dimensional photoacoustic imaging system, using a 15 MHz linear ultrasound array. Using a black leaf skeleton as a complex absorbing structure, we demonstrate that the photoacoustic transmission matrix approach allows to reveal structural features that are invisible in conventional photoacoustic images, as well as to selectively control light focusing on absorbing targets, leading to a local enhancement of the photoacoustic signal.
    Optics Letters 05/2014; 39(9):2664-2667. · 3.39 Impact Factor
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    ABSTRACT: We investigate experimentally the use of speckle illumination for photoacoustic imaging. In particular, we demonstrate that otherwise invisible features are revealed through high-frequency signals fluctuations from different speckle realizations.
    Biomedical Optics; 04/2014
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    ABSTRACT: Imaging with optical resolution through and inside complex samples is a difficult challenge with important applications in many fields. The fundamental problem is that inhomogeneous samples, such as biological tissues, randomly scatter and diffuse light, impeding conventional image formation. Despite many advancements, no current method enables to noninvasively image in real-time using diffused light. Here, we show that owing to the memory-effect for speckle correlations, a single image of the scattered light, captured with a standard high-resolution camera, encodes all the information that is required to image through the medium or around a corner. We experimentally demonstrate single-shot imaging through scattering media and around corners using incoherent light and various samples, from white paint to dynamic biological samples. Our lensless technique is simple, does not require laser sources, wavefront-shaping, nor time-gated detection, and is realized here using a camera-phone. It has the potential to enable imaging in currently inaccessible scenarios.
    03/2014;
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    ABSTRACT: The recent theory of compressive sensing leverages upon the structure of signals to acquire them with much fewer measurements than was previously thought necessary, and certainly well below the traditional Nyquist-Shannon sampling rate. However, most implementations developed to take advantage of this framework revolve around controlling the measurements with carefully engineered material or acquisition sequences. Instead, we use the natural randomness of wave propagation through multiply scattering media as an optimal and instantaneous compressive imaging mechanism. Waves reflected from an object are detected after propagation through a well-characterized complex medium. Each local measurement thus contains global information about the object, yielding a purely analog compressive sensing method. We experimentally demonstrate the effectiveness of the proposed approach for optical imaging by using a 300-micrometer thick layer of white paint as the compressive imaging device. Scattering media are thus promising candidates for designing efficient and compact compressive imagers.
    Scientific reports. 01/2014; 4:5552.
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    ABSTRACT: This paper was published in Optics Letters and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OL.38.005188 . Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law. ------------------------------------------------------------------------------------------------------------------ In high-frequency photoacoustic imaging with uniform illumination, homogeneous photoabsorbing structures may be invisible because of their large size or limited-view issues. Here we show that, by exploiting dynamic speckle illumination, it is possible to reveal features that are normally invisible with a photoacoustic system comprised of a 20 MHz linear ultrasound array. We demonstrate imaging of a ∅5 mm absorbing cylinder and a 30 μm black thread arranged in a complex shape. The hidden structures are directly retrieved from photoacoustic images recorded for different random speckle illuminations of the phantoms by assessing the variation in the value of each pixel over the illumination patterns.
    Optics Letters 12/2013; 38(23):5188-91. · 3.39 Impact Factor
  • 11/2013; 24(12).
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    ABSTRACT: We experimentally and numerically study the potential of photoacoustic-guiding for light focusing through scattering samples via wavefront-shaping and iterative optimization. We experimentally demonstrate that the focusing efficiency on an extended absorber can be improved by iterative optimization of the high frequency components of the broadband photoacoustic signal detected with a spherically focused transducer. We demonstrate more than 8-fold increase in the photoacoustic signal generated by a 30 microns wire using a narrow frequency band around 60MHz. We numerically confirm that such optimization leads to a smaller optical focus than using the low frequency content of the photoacoustic feedback.
    10/2013;
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    ABSTRACT: We demonstrate how to measure accurately the transmission matrix of a complex medium. With this information, we show how to focus light, recover an image, and even perform efficient reconstruction of a sparse object.
    Computational Optical Sensing and Imaging; 06/2013
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    ABSTRACT: Optical wavefront-shaping has emerged as a powerful tool to manipulate light in strongly scattering media. It enables diffraction-limited focusing and imaging at depths where conventional microscopy techniques fail. However, while most wavefront-shaping works to-date exploited direct access to the target or implanted probes, the challenge is to apply it non-invasively inside complex samples. Ultrasonic-tagging techniques have been recently demonstrated but these require a sequential point-by- point acquisition, a major drawback for imaging applications. Here, we introduce a novel approach to non-invasively measure the optical transmission-matrix inside a scattering medium, exploiting the photo-acoustic effect. Our approach allows for the first time to simultaneously discriminate, localize, and selectively focus light on multiple targets inside a scattering sample, as well as to recover and exploit the scattering medium properties. Combining the powerful approach of the transmission-matrix with the advantages of photoacoustic imaging opens the path towards deep-tissue imaging and light-delivery utilizing endogenous optical contrast.
    05/2013;
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    ABSTRACT: The measurement of the polychromatic transmission matrix of a multiply scattering medium is reported, thus allowing control the propagation of an ultrashort pulse through the medium. We also report on our effort towards fast transmission matrix measurement.
    Novel Techniques in Microscopy; 04/2013
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    ABSTRACT: Focusing light through dynamically varying heterogeneous media is a sought-after goal with important applications ranging from free-space communication to nano-surgery. The underlying challenge is to control the optical wavefront with a large number of degrees-of-freedom (DOF) at timescales shorter than the medium dynamics. Recently, many advancements have been reported following the demonstration of focusing through turbid samples by wavefront-shaping, using spatial light modulators (SLMs) having >1000 DOF. Unfortunately, SLM-based wavefront-shaping requires feedback from a detector/camera and is limited to slowly-varying samples. Here, we demonstrate a novel approach for wavefront-shaping using all-optical feedback. We show that the complex wavefront required to focus through highly scattering samples, including thin biological tissues, can be generated at sub-microsecond timescales by the process of field self-organization inside a multimode laser cavity, without requiring electronic feedback or SLMs. This wavefront-shaping mechanism is more than five orders of magnitude faster than state-of-the-art, reaching the timescales required in many applications.
    Nature Photonics 03/2013; 7(11). · 27.25 Impact Factor
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    ABSTRACT: We show that the polarization state of coherent light propagating through an optically thick multiple scattering medium can be controlled by wavefront shaping, that is, by controlling only the spatial phase of the incoming field with a spatial light modulator. Any polarization state of light at any spatial position behind the scattering medium can be attained with this technique. Thus, transforming the random medium to an arbitrary optical polarization component becomes possible.
    Optics Letters 11/2012; 37(22):4663-5. · 3.39 Impact Factor
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    ABSTRACT: We show that wavefront-shaping enables spatial, temporal, spectral and polarization control of light in random media. We demonstrate real-time imaging ‘around corners’ and through turbid layers and focusing of ultrashort pulses in an epi-illumination microscope.
    Frontiers in Optics; 10/2012
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    ABSTRACT: A random medium can serve as a controllable arbitrary spectral filter with spectral resolution determined by the inverse of the interaction time of the light in the medium. We use wavefront shaping to implement an arbitrary spectral response at a particular point in the scattered field. We experimentally demonstrate this technique by selecting either a narrow band or dual bands with a width of 5.5 nm each.
    Optics Letters 08/2012; 37(16):3429-31. · 3.39 Impact Factor
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    ABSTRACT: Imaging with optical resolution through turbid media is a long sought-after goal with important applications in deep tissue imaging. Although extensively studied, this goal was considered impractical until recently. Adaptive-optics techniques, which can correct weak aberrations, are inadequate for turbid samples, where light is scattered to complex speckle patterns with a number of modes greatly exceeding the number of degrees of control. This conception changed after the demonstration of coherent focusing through turbid media by wavefront-shaping, using spatial light modulators. Here, we show that wavefront-shaping enables wide-field imaging through turbid layers with incoherent illumination, and imaging of occluded objects using light scattered from diffuse walls. In contrast to the recently introduced schemes for imaging through turbid media, our technique does not require coherent sources, interferometric detection, raster-scanning or off-line reconstruction. Our results bring wavefront-shaping closer to practical applications and realize the vision of looking through `walls' and around corners.
    Nature Photonics 08/2012; 6(8):549-553. · 27.25 Impact Factor
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    ABSTRACT: We analyze the spatiotemporal distortions of an ultrashort pulse focused through a thin scattering surface. We show and experimentally verify that in such a scenario temporal distortions are proportional to the distance from the optical axis and are present only outside the focal point, as result of geometrical path length differences. We use wavefront shaping to correct for the spatiotemporal distortions and to temporally compress chirped input pulses through the scattering medium.
    Optics Express 02/2012; 20(5):5189-95. · 3.55 Impact Factor
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    ABSTRACT: Imaging with optical resolution through highly scattering media is a long sought-after goal with important applications in deep tissue imaging. Although being the focus of numerous works, this goal was considered impractical until recently. Adaptive-optics techniques which are effective in correcting weak wavefront aberrations, were deemed inadequate for turbid samples, where complex speckle patterns arise and light is scattered to a large number of modes that greatly exceeds the number of degrees of control. This conception changed after the demonstration of focusing coherent light through turbid media by wavefront-shaping, using a spatial-light-modulator (SLM). Here we show that wavefront-shaping enables widefield real-time imaging through scattering media with both coherent or incoherent illumination, in transmission and reflection. In contrast to the recently introduced schemes for imaging through turbid media, our technique does not require coherent sources, interferometric detection, raster scanning, or off-line image reconstruction. Our results bring wavefront-shaping closer to practical applications, and realize the vision of looking 'through walls' and 'around corners'.
    02/2012;
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    ABSTRACT: A new concept for focusing light through a randomly disordered media is demonstrated. Results show how by placing the randomly scattering media directly into a laser cavity tight focusing is accomplished in less than 600ns.
    Lasers and Electro-Optics (CLEO), 2012 Conference on; 01/2012
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    ABSTRACT: We demonstrate single-beam coherent anti-Stokes Raman spectroscopy (CARS), for detecting and identifying traces of solids, including minute amounts of explosives, from a standoff distance (>50 m) using intense femtosecond pulses. Until now, single-beam CARS methods relied on pulse-shapers in order to obtain vibrational spectra. Here we present a simple and easy-to-implement detection scheme, using a commercially available notch filter, that does not require the use of a pulse-shaper.
    Applied Physics Letters 11/2011; 100(5). · 3.79 Impact Factor

Publication Stats

204 Citations
141.22 Total Impact Points

Institutions

  • 2013
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
  • 2008–2012
    • Weizmann Institute of Science
      • Department of Physics of Complex Systems
      Israel
  • 2006
    • Soreq Nuclear Research Center
      Yerushalayim, Jerusalem District, Israel