Frequency width of open channels in multiple scattering media

Abstract

We report optical measurements of the spectral width of open transmission channels in a three-dimensional diffusive medium. The light transmission through a sample is enhanced by efficiently coupling to open transmission channels using repeated digital optical phase conjugation. The spectral properties are investigated by enhancing the transmission, fixing the incident wavefront and scanning the wavelength of the laser. We measure the transmitted field to extract the field correlation function and the enhancement of the total transmission. We find that optimizing the total transmission leads to a significant increase in the frequency width of the field correlation function. Additionally we find that the enhanced transmission persists over an even larger frequency bandwidth. This result shows open channels in the diffusive regime are spectrally much wider than previous measurements in the localized regime suggest.

Angular Memory Effect of Transmission Eigenchannels

“…Such variations can be explained qualitatively by a perturbation model that describes the robustness of the eigenchannels against perturbations such as a sample tilt or an incident wavefront tilt. Our model can be extended to other perturbations, such as frequency detuning of an incident light, and provides a qualitative understanding of the enhanced bandwidth (spectral memory effect) for high-transmission channels, which was observed previously [29]. Therefore our work reveals the general characteristic of high-transmission channels: their transmitted fields are robust while their reflected fields are sensitive against perturbations.…”

“…The key ingredient that enabled this strategic shift is the hidden correlations of seemingly random speckles formed by interference of scattered light [11][12][13][14][15][16][17][18][19][20][21][22][23]. Quite remarkably, such correlations have been both predicted and observed in the angular, spectral, spatial, and temporal domains [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38].…”

Blind focusing through strongly scattering media using wavefront shaping with nonlinear feedback

“…b . In this case, after performing the wavefront shaping algorithm multiple times, E (k) b will converge to the eigenvector of matrix T with the highest eigenvalue [15]. In other words, instead of forming a focus, the algorithm will instead optimize the total transmission through the scattering sample.…”

“…Performing multiple iterations of wavefront can therefore ultimately result in a focus being formed at one of the targets. will converge to the eigenvector of matrix T with the highest eigenvalue [15]. In other words, instead of forming a focus, the algorithm will instead optimize the total transmission through the scattering sample.…”

Transverse localization of transmission eigenchannels

“…In a lossless diffusive medium, the transmission eigenvalues τ span from 0 to 1, leading to closed (τ ≈ 0) and open (τ ≈ 1) channels. In recent years, spatial light modulators (SLMs) have been used to excite the open channels [5][6][7][8][9][10][11][12][13][14] to enhance light transmission through diffusive media. Selective excitation of individual channels can dramatically change the total energy stored inside the random media as well as the spatial distribution of energy density [14][15][16][17][18][19][20].However, some important questions regarding the transmission eigenchannels remain open.…”