Research perspective: Nature - Anti reflective film | Metasurface
In disordered media, electromagnetic wave scattering of waves is an important limiting step in a range of engineering applications, including telecommunications, biomedical imaging, seismology, and materials engineering. Even in opaque media, wavefront shaping technology can reduce the impact of wave scattering by designing specific modes (known as open transmission eigenchannels), through which electromagnetic waves can pass through disordered media without any backward reflection. However, due to the rarity of such channels, it is currently not possible to perfectly transmit any incident light field through opaque samples.
Today, Michael Horodynski and Matthieu Davy from Stefan Rotter's team at Vienna University of Technology (TU Wien) in Austria published a paper in Nature, demonstrating a randomly disordered medium that is semi transparent to all incident light waves when a customized complementary medium is placed in front of it. Therefore, the reflection matrices of the two media surfaces facing each other need to satisfy the matrix extension of critical coupling conditions. This method has been implemented both numerically and experimentally, and has been used to design electromagnetic waveguides with dozens of scattering elements placed inside. This semi transparent scattering medium can also store incident radiation inside for a long time.
Figure 1: Conceptual Explanation.
Figure 2: Disordered fully propagating waveguide.
Figure 4: Energy stored within the sample
Figure 4: Energy stored within the sample
This study has theoretically and experimentally demonstrated that by placing optimized complementary media in front of a disordered medium, the disordered medium can be fully transmitted to all incident wavefronts. Due to the fact that only the reflection matrix of this complementary medium must be carefully designed, thin metasurfaces can be used for this purpose, enabling the creation of customized and potentially time adaptive anti reflection structures, and their application in wireless communication, filtering, energy harvesting, and imaging fields. In the long run, advances in computing power and microfabrication will make this method applicable to an increasing number of pattern systems.
Editor: Sichuan Jinzhongde Science and Technology Research Institute
