Coherent light propagation in random scattering media such as biological tissue, fog, and turbulent atmosphere is dictated by the eigenchannels of transmission matrices. The spatial profiles of these channels can be exploited for tailoring light-matter interactions inside a turbid medium. While the spatial structures of transmission eigenchannels in diffusive waveguides are extensively studied, most scattering systems in practical applications have an open slab geometry. Here, we present experimental and numerical studies on the spatial profiles of transmission eigenchannels in disordered slabs of thickness much less than the width. We discover that all transmission eigenchannels are localized in the transverse direction (parallel to the slab). The lateral dimension of each channel increases linearly with the slab thickness and the transport mean free path. Such localization, which are absent for the transmission eigenchannels in quasi-one-dimensional samples, originate from spatial disorder, partial mixing of spatial channels, and non-local correlations of waves in the slab. Experimentally not all input channels can be controlled, and usually only the phase of incident beam is modulated. In this case, light injected to a high-transmission channel remains laterally localized, but the beam in a low-transmission eigenchannel expands laterally as it propagates through the slab. Our results provide physical insight to the transmission eigenchannels in open disordered systems, therefore paving the way for their applications in optical imaging and communication.
Hasan Yilmaz, Chia Wei Hsu, Alexey Yamilov, and Hui Cao, "Transverse localization of transmission Eigenchannels (Conference Presentation)," Proc. SPIE 10502, Adaptive Optics and Wavefront Control for Biological Systems IV, 105020V (Presented at SPIE BiOS: January 28, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2288767.5751623731001.
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