Far-Field Wavefront Control of Nonlinear Luminescence in Disordered Gold Metasurfaces.
Roubaud, G., P. Bondareff, G. Volpe, S. Gigan, S. Bidault, and S. Grésillon.
Nano Letters 20, no. 5 (2020): 3291-3298.
Résumé: We demonstrate the local optimization of nonlinear luminescence from disordered gold metasurfaces by shaping the phase of femtosecond excitation. This process is enabled by the far-field wavefront control of plasmonic modes delocalized over the sample surface, leading to a coherent enhancement of subwavelength electric fields. In practice, the increase in nonlinear luminescence is strongly sensitive to both the nanometer-scale morphology and the level of structural complexity of the gold metasurface. We typically observe a 2 orders of magnitude enhancement of the luminescence signal for an optimized excitation wavefront compared to a random one. These results demonstrate how disordered metasurfaces made of randomly coupled plasmonic resonators, together with wavefront shaping, provide numerous degrees of freedom to program locally optimized nonlinear responses and optical hotspots.
Mots-clés: disordered media; metasurfaces; nonlinear luminescence; plasmonics; Wavefront shaping
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Influence of the Local Scattering Environment on the Localization Precision of Single Particles.
Bouchet, D., R. Carminati, and A. P. Mosk.
Physical Review Letters 124, no. 13 (2020): 133903.
Résumé: We study the fundamental limit on the localization precision for a subwavelength scatterer embedded in a strongly scattering environment, using the external degrees of freedom provided by wavefront shaping. For a weakly scattering target, the localization precision improves with the value of the local density of states at the target position. For a strongly scattering target, the localization precision depends on the dressed polarizability that includes the backaction of the environment. This numerical study provides new insights for the control of the information content of scattered light by wavefront shaping, with potential applications in sensing, imaging, and nanoscale engineering.
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Real-time non-contact cellular imaging and angiography of human cornea and limbus with common-path full-field/SD OCT.
Mazlin, V., P. Xiao, J. Scholler, K. Irsch, K. Grieve, M. Fink, and A. C. Boccara.
Nature Communications 11, no. 1 (2020).
Résumé: © 2020, The Author(s). In today’s clinics, a cell-resolution view of the cornea can be achieved only with a confocal microscope (IVCM) in contact with the eye. Here, we present a common-path full-field/spectral-domain OCT microscope (FF/SD OCT), which enables cell-detail imaging of the entire ocular surface in humans (central and peripheral cornea, limbus, sclera, tear film) without contact and in real-time. Real-time performance is achieved through rapid axial eye tracking and simultaneous defocusing correction. Images contain cells and nerves, which can be quantified over a millimetric field-of-view, beyond the capability of IVCM and conventional OCT. In the limbus, palisades of Vogt, vessels, and blood flow can be resolved with high contrast without contrast agent injection. The fast imaging speed of 275 frames/s (0.6 billion pixels/s) allows direct monitoring of blood flow dynamics, enabling creation of high-resolution velocity maps. Tear flow velocity and evaporation time can be measured without fluorescein administration.
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Diagnostic Accuracy of Four Levels of Manual Compression Applied in Supersonic Shear Wave Elastography of the Breast.
Chamming's, F., C. Hangard, J.-L. Gennisson, C. Reinhold, and L. S. Fournier.
Academic Radiology (2020).
Résumé: © 2020 The Association of University Radiologists Purpose: To investigate the diagnostic accuracy of applying four levels of manual pressure in Shear Wave Elastography (SWE) of the breast and to assess inter-rater reliability. Materials and Methods: Single-center prospective preliminary study including patients receiving ultrasound examination of breast lesions as part of routine clinical practice. SWE was performed on 60 breast masses (26 benign and 34 malignant) in 54 patients by a breast fellowship trained radiologist. Stiffness values were compared between benign and malignant masses at four levels of manual compression: none, mild, moderate, and marked. Accuracy of SWE was assessed using receiving operating characteristics analysis at each level. In 18 patients, a second radiologist repeated the SWE acquisitions to evaluate reproducibility. Reproducibility was assessed using intraclass correlation coefficient. Results: Without compression, we observed no significant difference in stiffness (p > 0.99) between benign and malignant lesions, and SWE demonstrated low accuracy (area under the curve = 0.64). Stiffness was higher in malignant lesions at all levels of compression (p < 0.001). SWE demonstrated good accuracy at all three levels of compression (from area under the curve = 0.71 to 0.84 across Emax and Emean), with high interobserver agreement. Conclusion: This preliminary study suggests that not using compression during SWE for breast lesion characterization offers suboptimal results. On the contrary, application of compression yields high diagnostic performance with good interobserver agreement and, as such, should be included in routine clinical practice.
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