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Search Results: 1 - 10 of 3022 matches for " Arthur Goetschy "
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Broadband Coherent Enhancement of Transmission and Absorption in Disordered Media
Chia Wei Hsu,Arthur Goetschy,Yaron Bromberg,A. Douglas Stone,Hui Cao
Physics , 2015, DOI: 10.1103/PhysRevLett.115.223901
Abstract: We study the optimal diffusive transmission and absorption of broadband or polychromatic light in a disordered medium. By introducing matrices describing broadband transmission and reflection, we formulate an extremal eigenvalue problem where the optimal input wavefront is given by the corresponding eigenvector. We show analytically that a single wavefront can exhibit strongly enhanced total transmission or total absorption across a bandwidth that is orders of magnitude broader than the spectral correlation width of the medium, due to long-range correlations in coherent diffusion. We find excellent agreement between the analytic theory and numerical simulations.
Coherent control of photocurrent in a disordered photovoltaic system
Seng Fatt Liew,Sebastien M. Popoff,Stafford W. Sheehan,Arthur Goetschy,Charles A. Schmuttenmaer,A. Douglas Stone,Hui Cao
Physics , 2015,
Abstract: Optical absorption is commonly considered an intrinsic property of a medium, independent of the details of the illumination source. However, for a spatially coherent illumination of a disordered medium, interference effects can modify the spatial distribution of light inside the medium, allowing the global or local absorption to be tuned by adjusting an input beam's spatial characteristics. Here we demonstrate the coherent control of absorption by using the wavefront shaping technique to modulate photocurrent in a dye-sensitized solar cell. The incident wavefront of a laser beam is optimized to concentrate light near the front side of the porous photoanode where the collection efficiency of photo-generated electrons is highest. Destructive interference reduces light leakage through open boundaries, facilitating light absorption and conversion to current. This technique provides a powerful tool for probing and controlling photochemical processes inside nominally opaque media by manipulating the internal spatial distribution of light intensity.
Towards a random laser with cold atoms
William Guerin,Nicolas Mercadier,Franck Michaud,Davide Brivio,Luis S. Froufe-Pérez,Rémi Carminati,Vitalie Eremeev,Arthur Goetschy,Sergey E. Skipetrov,Robin Kaiser
Physics , 2009, DOI: 10.1088/2040-8978/12/2/024002
Abstract: Atoms can scatter light and they can also amplify it by stimulated emission. From this simple starting point, we examine the possibility of realizing a random laser in a cloud of laser-cooled atoms. The answer is not obvious as both processes (elastic scattering and stimulated emission) seem to exclude one another: pumping atoms to make them behave as amplifier reduces drastically their scattering cross-section. However, we show that even the simplest atom model allows the efficient combination of gain and scattering. Moreover, supplementary degrees of freedom that atoms offer allow the use of several gain mechanisms, depending on the pumping scheme. We thus first study these different gain mechanisms and show experimentally that they can induce (standard) lasing. We then present how the constraint of combining scattering and gain can be quantified, which leads to an evaluation of the random laser threshold. The results are promising and we draw some prospects for a practical realization of a random laser with cold atoms.
Non-Hermitian Euclidean random matrix theory
A. Goetschy,S. E. Skipetrov
Physics , 2011, DOI: 10.1103/PhysRevE.84.011150
Abstract: We develop a theory for the eigenvalue density of arbitrary non-Hermitian Euclidean matrices. Closed equations for the resolvent and the eigenvector correlator are derived. The theory is applied to the random Green's matrix relevant to wave propagation in an ensemble of point-like scattering centers. This opens a new perspective in the study of wave diffusion, Anderson localization, and random lasing.
Eigenvalue distributions of large Euclidean random matrices for waves in random media
S. E. Skipetrov,A. Goetschy
Physics , 2010, DOI: 10.1088/1751-8113/44/6/065102
Abstract: We study probability distributions of eigenvalues of Hermitian and non-Hermitian Euclidean random matrices that are typically encountered in the problems of wave propagation in random media.
Euclidean random matrices and their applications in physics
A. Goetschy,S. E. Skipetrov
Physics , 2013,
Abstract: We review the state of the art of the theory of Euclidean random matrices, focusing on the density of their eigenvalues. Both Hermitian and non-Hermitian matrices are considered and links with simpler, standard random matrix ensembles are established. We discuss applications of Euclidean random matrices to contemporary problems in condensed matter physics, optics, and quantum chaos.
Euclidean matrix theory of random lasing in a cloud of cold atoms
A. Goetschy,S. E. Skipetrov
Physics , 2011, DOI: 10.1209/0295-5075/96/34005
Abstract: We develop an ab initio analytic theory of random lasing in an ensemble of atoms that both scatter and amplify light. The theory applies all the way from low to high density of atoms. The properties of the random laser are controlled by an Euclidean matrix with elements equal to the Green's function of the Helmholtz equation between pairs of atoms in the system. Lasing threshold and the intensity of laser emission are calculated in the semiclassical approximation. The results are compared to the outcome of the diffusion theory of random lasing.
Filtering Random Matrices: The Effect of Incomplete Channel Control in Multiple Scattering
A. Goetschy,A. D. Stone
Physics , 2013, DOI: 10.1103/PhysRevLett.111.063901
Abstract: We present an analytic random matrix theory for the effect of incomplete channel control on the measured statistical properties of the scattering matrix of a disordered multiple-scattering medium. When the fraction of the controlled input channels, m1, and output channels, m2, is decreased from unity, the density of the transmission eigenvalues is shown to evolve from the bimodal distribution describing coherent diffusion, to the distribution characteristic of uncorrelated Gaussian random matrices, with a rapid loss of access to the open eigenchannels. The loss of correlation is also reflected in an increase in the information capacity per channel of the medium. Our results have strong implications for optical and microwave experiments on diffusive scattering media.
Transmission of quantum entanglement through a random medium
M. Candé,A. Goetschy,S. E. Skipetrov
Physics , 2014, DOI: 10.1209/0295-5075/107/54004
Abstract: We study the high-dimensional entanglement of a photon pair transmitted through a random medium. We show that multiple scattering in combination with the subsequent selection of only a fraction of outgoing modes reduces the average entanglement of an initially maximally entangled two-photon state. Entanglement corresponding to a random pure state is obtained when the number of modes accessible in transmission is much less than the number of modes in the incident light. An amount of entanglement approaching that of the incident light can be recovered by accessing a larger number of transmitted modes. In contrast, a pair of photons in a separable state does not gain any entanglement when transmitted through a random medium.
Optimal Recovery of Holomorphic Functions from Inaccurate Information about Radial Integration  [PDF]
Arthur DeGraw
American Journal of Computational Mathematics (AJCM) , 2012, DOI: 10.4236/ajcm.2012.24035
Abstract: This paper addresses the optimal recovery of functions from Hilbert spaces of functions on the unit disc. The estimation, or recovery, is performed from inaccurate information given by integration along radial paths. For a holomorphic function expressed as a series, three distinct situations are considered: where the information error in L2 norm is bound by δ>0 or for a finite number of terms the error in l2N norm is bound by δ>0 or lastly the error in the jth coefficient is bound by δj>0. The results are applied to the Hardy-Sobolev and Bergman-Sobolev spaces.
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