One-way light flow by spatio-temporal modulation

The unidirectional flow of electrons that takes place in a conventional electronic diode has been a cornerstone in the development of the field of electronics. Achieving an equivalent one-way flow for light has been a long-standing problem. While a number of concepts have been suggested recently, attaining a unidirectional flow of light in a two-port system (e.g., a waveguiding configuration) is still challenging. Here, we present what we believe to be a novel approach for breaking reciprocity and achieving one-way flow of light. Taking a nanoplasmonic waveguide as an example, we show that a combination of time-dependent interband optical transitions, when in systems exhibiting a backward wave flow, can yield light transmission strictly in one direction. In our configuration, the energy flow is unidirectional: light is fully reflected in one direction of propagation, and is unperturbed in the other. The concept can find use in a range of applications including communications, smart windows, thermal radiation management, and solar energy harvesting.

Automated summary

The unidirectional flow of electrons in a conventional electronic diode has played a crucial role in the development of electronics. However, achieving a one-way flow of light has been a long-standing problem. This study presents a novel approach to break reciprocity and achieve a unidirectional flow of light using a nanoplasmonic waveguide as an example. By combining time-dependent interband optical transitions, a strict one-way light transmission can be achieved in systems with a backward wave flow. This concept has various applications in communication, smart windows, thermal radiation management, and solar energy harvesting.