Guided reading：
The University of W ü rzburg collaborated with physicists at Rostock University to develop an optical funnel device. Using the physical mechanism of the “non-Hermitian skin effect”, the research team led by Professor AlexanderSzameit of Rostock University can focus the light signal in the 10-kilometer-long optical fiber at a specific point, realizing the “optical funnel”. It can be used as a new platform for hypersensitive optical detectors. Professor Ronny Thomale is a professor of theoretical condensed matter physics at Julius-Maximilian University in W ü rzburg. Discovering and theoretically describing new quantum states of matter is one of his main research areas. “in the practice of theoretical physicists, it is one of the most exciting moments to develop a theory for a new physical phenomenon and then look for new experiments to stimulate this effect,” he said. “
Research background：
Topological matter has become one of the most active fields in modern physics.The term topology, which comes from ancient Greek and means “learning” and “place” , is a mathematics-based discipline that has now spread widely to physics, including optics.Topological materials, together with other synthetic materials, form a broader research direction —— — Topological metamaterials.Not content with the physical and chemical ingredients provided by nature, physicists have developed synthetic crystals consisting of artificially tailored degrees of freedom.The light funnel, developed by Thomale and Szameit, selects a topological fiber that conducts light along the fiber while allowing detailed spatial resolution.When we deal with periodic systems, it is often approximated as “infinite expansion” , because small changes at the boundary do not cause obvious deviation of the system.However, it has recently been proposed that when the non-hermitian properties in some systems are not caused by gain and loss, but by the presence of an interface in an anisotropic lattice leading to the localization of all eigenmodes at that interface, this phenomenon is called “non-hermite skin effect” .This effect has caused a heated debate in non-hermite topological systems about the validity of body boundary corresponding to BBC. BBC is an important concept in topological physics, which requires bodies and boundaries coexist, and the quantity of bodies can be used to predict the properties of boundaries.The team achieved a non hermite photonic lattice by controlling for anisotropic coupling. The appearance of the interface leads to the collapse of the whole intrinsic mode spectrum and the exponential localization of all modes on the interface.Therefore, any light field in the LATTICE, regardless of its shape and input position, moves towards this interface, a topological phenomenon known as “non-hermite skin effect” .Based on this phenomenon, the team demonstrated an efficient light funnel that can focus light signals from a 10 kilometer long fiber at a specific point and can be applied to highly sensitive optical detectors.
Innovative Research：-Focusing the light signal in a 10-kilometer-long fiber
The team achieved an effect known as the “optical funnel”: based on the “non-Hermitian skin effect”, light signals in a 10-kilometer-long optical fiber can be focused at a specific point in the wire. The specific method is as follows: by controlling the anisotropic coupling in the optical fiber loop, the lattice is connected with different directions of anisotropy to produce the funnel effect of light. this effect depends on the non-Hermite skin effect caused by anisotropic coupling and its non-trivial topological characteristics. This work enables people to understand the skin effect in the framework of the topological state of matter. The team compared two models: 1 Hermite SSH model (Fig. 2A), consisting of nearest neighbor coupled lattice chains with alternating coupling constants, with alternating, isotropic coupling, as shown by the different shadows of the orange arrows. (2) the skin effect model (figure 2B), with alternating, anisotropic coupling, indicated by black arrows of different sizes, this anisotropy leads to non-Hermitian.
