Dr. Maïmouna Bocoum Profile

Dr. Maïmouna Bocoum

Researcher at Institut Langevin

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Publications (7)

Proceedings Article | 12 March 2024 Poster + Paper

Fourier transform acousto-optic imaging: toward real-time imaging of thick biological media

François Figliolia, Qin Liu, Sylvie Janicot, Gaëlle Lucas-Leclin, Jean-Pierre Huignard, François Ramaz, Jean-Michel Tualle, Maïmouna Bocoum

Proceedings Volume 12842, 1284217 (2024) https://doi.org/10.1117/12.3003141

KEYWORDS: Adaptive optics, Acoustooptics, Cameras, Photons, Biological imaging, Laser scattering, Scattering media, Real time imaging, Laser sources, Fourier transforms

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Proceedings Article | 9 March 2023 Presentation

Fourier-transform acousto-optic imaging

Maïmouna Bocoum

Proceedings Volume PC12379, PC1237915 (2023) https://doi.org/10.1117/12.2648033

KEYWORDS: Acousto-optics, Photons, Tissues, Tissue optics, Modulation, Light scattering, In vivo imaging, Speckle, Scattering, Infrared imaging

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Proceedings Article | 14 May 2019 Presentation

Laser wakefield acceleration driven by few-cycle pulses on plasma mirrors (Conference Presentation)

Neil Zaïm, Frederik Böhle, Maïmouna Bocoum, Aline Vernier, Stefan Haessler, Xavier Davoine, Laurent Videau, Jérôme Faure, Rodrigo López-Martens

Proceedings Volume 11037, 110370E (2019) https://doi.org/10.1117/12.2520802

KEYWORDS: Plasma, Electrons, Mirrors, Pulsed laser operation, Laser optics, Reflection, Solids, Silica, Tunable lasers, Interfaces

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We study both experimentally and numerically the emission of energetic electrons during the reflection of a relativistic few-cycle laser pulse off a plasma mirror with controlled electron density gradient. A weak prepulse is used to trigger plasma expansion on a solid density target (optical grade fused silica) and electron emission is measured for different plasma scale lengths using a time-delayed relativistic-intensity few-cycle laser pulse with duration tunable from 24fs down to 3.5fs (1.5 cycle at the 719-nm carrier wave). Two distinct acceleration regimes are identified, for which the electron ejection mechanisms are radically different. On the one hand, when the plasma-vacuum interface is sharp, an attosecond electron bunch is emitted from the plasma at each laser optical cycle [1,2]. These electrons can then be efficiently accelerated in vacuum by the reflected laser field (vacuum laser acceleration or VLA) [3]. On the other hand, when the plasma scale length is larger, on the scale of a few laser wavelengths, a different regime is identified in which we observe what appears to be a collimated laser wakefield accelerated electron beam. Back-acceleration of energetic electrons can be explained by ionization injection of the rotating plasma waves inside the inhomogeneous electron density gradient formed at the plasma mirror surface [4]. These electrons are only detected when the laser pulse duration is shorter than 10 fs, clearly showing that new and unexpected laser-plasma interaction regimes become observable in the few-cycle regime. [1] M. Bocoum et al., Anti-correlated emission of high harmonics and fast electron beams from plasma mirrors, Physical Review Letters 116, 185001 (2016) [2] M. Thévenet et al., On the physics of electron ejection from laser-irradiated overdense plasmas, Physics of Plasmas 23, 063119 (2016) [3] M. Thévenet, et al. Vacuum laser acceleration of relativistic electrons using plasma mirror injectors, Nature Physics 12, 355–360 (2015) [4] N. Zaïm, et al. Laser wakefield acceleration driven by few-cycle laser pulses in overdense plasmas, manuscript in preparation

Proceedings Article | 24 May 2018 Presentation

Ultranarrow spectral filter for acousto-optic imaging for medical applications (Conference Presentation)

Caroline Venet, Maïmouna Bocoum, Thierry Chanelière, François Ramaz, Anne Louchet-Chauvet

Proceedings Volume 10677, 106771N (2018) https://doi.org/10.1117/12.2303511

KEYWORDS: Acousto-optics, Optical filters, Medical imaging, Crystals, Ultrasonography, Tissues, Modulation, Hole burning spectroscopy, Real time imaging, Liver

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Nowadays imaging the early liver metastases has to be improved in order to have an easier setup than MRI or to be more discriminant than ultrasound between healthy and diseased tissues. Acousto-optic imaging could solve these issues by coupling itself with ultrasound modality: the additional optical contrast would suppress the indetermination on the health of the biological tissue. Acousto-optic imaging is a multi-wave technique which localizes light in very scattering media thanks to an acoustic wave: the acousto-optic effect creates frequency-shifted light, carrying local information about the insonified volume. The central challenge of acousto-optic imaging is the detection of the frequency-shifted light, because there are only very few modulated photons and they create a speckle pattern. We choose to explore the detection by spectral filtering using the spectral hole burning process in rare earth doped crystal [1]. Spectral hole burning consists in creating a sub-MHz-wide transparency window in the wide absorption spectrum of a rare earth doped crystal: the crystal becomes transparent at the wavelength of the spectral hole and thus can filter the modulated light. This filtering technique is intrinsically immune to speckle decorrelation and therefore well adapted to in vivo imaging. We use a YAG crystal doped with thulium ions under a magnetic field which increases the lifetime of the spectral hole from 10ms to longer than a minute. We have undertaken a spectroscopic study to optimize the hole preparation sequence. The long lifetime simplifies the optimization of fast imaging sequences, making real-time acousto-optic imaging reachable. We will present the first acousto-optic images achieved with a long-lived spectral filter in Tm:YAG, in a scattering medium. [1] Li, Y., Zhang, H., Kim, C., Wagner, K. H., Hemmer, P., & Wang, L. V. (2008). Pulsed ultrasound-modulated optical tomography using spectral-hole burning as a narrowband spectral filter. Applied physics letters, 93(1), 011111.

Proceedings Article | 15 March 2018 Presentation

Acousto-optic imaging using plane waves (Conference Presentation)

Maïmouna Bocoum, Jean-Baptiste Laudereau, Alexander Grabar, Caroline Venet, Jean-Luc Gennisson, Clément Dupuy, Mickaël Tanter, François Ramaz

Proceedings Volume 10494, 104941Q (2018) https://doi.org/10.1117/12.2288327

KEYWORDS: Ultrasonography, Acousto-optics, Photons, Image restoration, Acoustics, Tomography, Multimodal imaging, Reconstruction algorithms, Ultrafast imaging, Radon

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Proceedings Article | 15 March 2018 Presentation

Ultra-thin spectral filter for acousto-optic imaging for medical applications (Conference Presentation)

Caroline Venet, Maïmouna Bocoum, Jean-Baptiste Laudereau, Thierry Chanelière, François Ramaz, Anne Louchet-Chauvet

Proceedings Volume 10494, 104941S (2018) https://doi.org/10.1117/12.2285841

KEYWORDS: Acousto-optics, Optical filters, Ultrasonography, Light scattering, Medical imaging, Hole burning spectroscopy, Spectroscopy, Tissues, Scattering, Crystals

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Proceedings Article | 14 March 2018 Presentation

Relativistic-intensity near-single-cycle laser system at 1 kHz (Conference Presentation)

Frederik Böhle, Andreas Blumenstein, Maïmouna Bocoum, Aline Vernier, Magali Lozano, Jean-Philippe Rousseau, Aurélie Jullien, Dominykas Gustas, Diego Guénot, Jérôme Faure, Máté Kovács, Martin Kretschmar, Peter Simon, Uwe Morgner, Tamás Nagy, Rodrigo López-Martens

Proceedings Volume 10511, 105111A (2018) https://doi.org/10.1117/12.2289088

KEYWORDS: Plasma, Extreme ultraviolet, Mirrors, Pulsed laser operation, Laser systems engineering, Femtosecond phenomena, Ultrafast phenomena, Waveguides, Capillaries, Fiber lasers

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