Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userEnergy density distribution of shaped waves inside scattering media mapped onto a complete set of diffusion modes
111
0
0.0
(
0
)
Added by
Oluwafemi Ojambati S.
Publication date
2016
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
We show that the spatial distribution of the energy density of optimally shaped waves inside a scattering medium can be described by considering only a few of the lowest eigenfunctions of the diffusion equation. Taking into account only the fundamental eigenfunction, the total internal energy inside the sample is underestimated by only 2%. The spatial distribution of the shaped energy density is very similar to the fundamental eigenfunction, up to a cosine distance of about 0.01. We obtained the energy density inside a quasi-1D disordered waveguide by numerical calculation of the joined scattering matrix. Computing the transmission-averaged energy density over all transmission channels yields the ensemble averaged energy density of shaped waves. From the averaged energy density obtained, we reconstruct its spatial distribution using the eigenfunctions of the diffusion equation. The results from our study have exciting applications in controlled biomedical imaging, efficient light harvesting in solar cells, enhanced energy conversion in solid-state lighting, and low threshold random lasers.
rate research
Read More
A grand challenge in fundamental physics and practical applications is overcoming wave diffusion to deposit energy into a target region deep inside a diffusive system. While it is known that coherently controlling the incident wavefront allows diffraction-limited focusing inside a diffusive system, in many applications targets are significantly larger than such a focus and the maximum deliverable energy remains unknown. Here, we introduce the deposition matrix, which maps an input wavefront to its internal field distribution, and theoretically predict the ultimate limitations on energy deposition at any depth. For example, the maximum obtainable energy enhancement occurs at 3/4 a diffusive systems thickness: regardless of its scattering strength. Experimentally we measure the deposition matrix and excite its eigenstates to enhance/suppress the energy within an extended target region. Our theoretical analysis reveals that such enhancement/suppression results from both selective transmission eigenchannel excitation and constructive/destructive interference among these channels.
A fundamental insight in the theory of diffusive random walks is that the mean length of trajectories traversing a finite open system is independent of the details of the diffusion process. Instead, the mean trajectory length depends only on the systems boundary geometry and is thus unaffected by the value of the mean free path. Here we show that this result is rooted on a much deeper level than that of a random walk, which allows us to extend the reach of this universal invariance property beyond the diffusion approximation. Specifically, we demonstrate that an equivalent invariance relation also holds for the scattering of waves in resonant structures as well as in ballistic, chaotic or in Anderson localized systems. Our work unifies a number of specific observations made in quite diverse fields of science ranging from the movement of ants to nuclear scattering theory. Potential experimental realizations using light fields in disordered media are discussed.
Significant enhancement of evanescent spatial harmonics inside the slabs of media with extreme optical anisotropy is revealed. This phenomenon results from the pumping of standing waves and has the feature of being weakly sensitive to the material losses. Such characteristics may enable subwavelength imaging at considerable distances away from the objects.
The newly emerging field of wave front shaping in complex media has recently seen enormous progress. The driving force behind these advances has been the experimental accessibility of the information stored in the scattering matrix of a disordered medium, which can nowadays routinely be exploited to focus light as well as to image or to transmit information even across highly turbid scattering samples. We will provide an overview of these new techniques, of their experimental implementations as well as of the underlying theoretical concepts following from mesoscopic scattering theory. In particular, we will highlight the intimate connections between quantum transport phenomena and the scattering of light fields in disordered media, which can both be described by the same theoretical concepts. We also put particular emphasis on how the above topics relate to application-oriented research fields such as optical imaging, sensing and communication.
This is the second of a series of papers devoted to develop a microscopical approach to the dipole emission process and its relation to coherent transport in random media. In this Letter, we deduce a relation between the transverse decay rate of an emitter in a virtual cavity and the complex refraction index of the host medium. We argue on the possibility of a criterion for inhibition/enhancement of spontaneous emission in function of the transition frequency and the correlation length of the host scatterers. In addition, we study the radiative/non-radiative nature of the net power emission through a microscopical analysis of the scattering events involved. This study reveals essential discrepancies with previous interpretations.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
