Researchers Develop New Way to Break Reciprocity Law
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Researchers develop new way to break reciprocity law:
An international research team lead by Aalto University has found a new and simple route to break the reciprocity law in the electromagnetic world, by changing a material's property periodically in time. The breakthrough could help to create efficient nonreciprocal devices, such as compact isolators and circulators, that are needed for the next generation of microwave and optical communications systems.
When we look through a window and see our neighbour on the street, the neighbour can also see us. This is called reciprocity, and it is the most common physical phenomenon in nature. Electromagnetic signals propagating between two sources is always governed by reciprocity law: if the signal from source A can be received by source B, then the signal from source B can also be received by source A with equal efficiency.
Researchers from Aalto University, Stanford University, and Swiss Federal Institute of Technology in Lausanne (EPFL) have successfully demonstrated [that] if the medium is shaped into an asymmetric structure and its physical property varies globally in time, the signal generated by source A can be received by source B but not the other way around. This creates a strong nonreciprocal effect, since the signal from Source B cannot be received by source A.
Traditionally, nonreciprocal devices have been made with relatively bulky magnets, which this process wouldn't need, leading to smaller devices useful even in situations where magnetism is harmful.
Journal Reference:
X. Wang, G. Ptitcyn, V.S. Asadchy, et al. Nonreciprocity in Bianisotropic Systems with Uniform Time Modulation, Physical Review Letters (DOI: 10.1103/PhysRevLett.125.266102)
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