Spatiotemporal Coherent Control of Light through a Multiple Scattering Medium with the Multispectral Transmission Matrix

Mickael Mounaix, Daria Andreoli, Hugo Defienne, Giorgio Volpe, Ori Katz, Samuel Grésillon, and Sylvain Gigan

Phys. Rev. Lett. 116, 253901 – Published 21 June 2016

Abstract

We report the broadband characterization of the propagation of light through a multiple scattering medium by means of its multispectral transmission matrix. Using a single spatial light modulator, our approach enables the full control of both the spatial and spectral properties of an ultrashort pulse transmitted through the medium. We demonstrate spatiotemporal focusing of the pulse at any arbitrary position and time with any desired spectral shape. Our approach opens new perspectives for fundamental studies of light-matter interaction in disordered media, and has potential applications in sensing, coherent control, and imaging.

Received 22 December 2015

DOI:https://doi.org/10.1103/PhysRevLett.116.253901

Physics Subject Headings (PhySH)

Light propagation, transmission & absorption Nonlinear optics

Atomic, Molecular & Optical

Authors & Affiliations

Mickael Mounaix^1,*, Daria Andreoli^1,2, Hugo Defienne¹, Giorgio Volpe^1,3, Ori Katz^1,2,4, Samuel Grésillon², and Sylvain Gigan¹

¹Laboratoire Kastler Brossel, ENS-PSL Research University, CNRS, UPMC Sorbonne Universités, Collège de France, 24 rue Lhomond, 75005 Paris, France
²Sorbonne Universités, UPMC Univ Paris 06, UMR 7587, Institut Langevin, 1 rue Jussieu, F-75005, Paris, France
³Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
⁴Department of Applied Physics, The Selim and Rachel Benin School of Computer Science and Engineering, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel

^*mickael.mounaix@lkb.ens.fr

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Issue

Vol. 116, Iss. 25 — 24 June 2016

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Images

Figure 1
Principle of the experiment. (a) Experimental setup. The laser (ultrashort pulse 110 fs at FWHM) is expanded and illuminates the SLM, which is conjugated with the back focal plane of a microscope objective. The scattering medium is a thick (around $100 μ m$ ) sample of ZnO nanoparticles, placed between two microscope objectives. The output plane is imaged on the two-photon fluorescence (2PF) sample. The long-pass filter (LPF) allows one to eliminate the autofluorescence of the ZnO. A dichroic mirror (DM) separates the two-photon fluorescence signal [imaged with an electron multiplying charge coupled device (EMCCD) camera] from the linear signal (imaged with a CCD). Lens ( $L$ ), pinhole (Ph), half plate wave (HPW), polarized beam splitter (PBS), delay line (DL), beam splitter (BS), polarizer ( $P$ ), band pass filter (BPF). (b) Temporal speckle from a single spatial speckle grain, obtained with an Interferometric Cross-Correlation (ICC) measurement. (c) ICC of the original pulse in the sample arm without the medium (dotted line), characterized by a time width of 520 fs at FWHM. ICC of the transmitted pulse through the medium, averaged over 100 different spatial positions of the speckle (solid line), characterized by a decay time of $≃ 2 ps$ (blue line).
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Figure 2
Spatiotemporal focusing with the MSTM, averaged over nine different spatial positions at the output. Spatiotemporal focusing is achieved by imposing a flat spectral phase at the output, whereas spatial focusing is obtained by focusing only the central wavelength of the pulse. The MSTM was measured at a delay-line position corresponding to the top arrow.
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Figure 3
Comparison of two-photon excitation for spatial (monochromatic phase conjugation) and spatiotemporal focusing, obtained with a thinner scattering sample of ZnO ( $τ_{m} ≃ 500 fs$ ). Inset: corresponding CCD signal. Integration time identical for both excitations: 2s for the two-photon excitation and 1 ms for the linear excitation. Scale bars normalized to the maximum intensity of spatiotemporal focusing. We observe a twofold enhancement of the nonlinear signal for the same average intensity when performing spatiotemporal focusing.
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Figure 4
Any suitable spectral shape can be obtained. (a) A negative spectral phase ramp advances the arrival time of the pulse. (b) A positive spectral phase ramp delays the pulse. (c) A $π$ -phase step in the spectral domain creates an odd pulse. (d) The sum of a flat phase pulse and a spectral phase ramp pulse gives two pulses with a controlled delay at the same output spatial position. Inset: spectral phase profile applied to the signals. The top arrows indicate the expected arrival time of the pulse.
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