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.& COPY; 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

The unidirectional flow of electrons in a conventional electronic diode has been crucial in electronics development. Achieving the same one-way flow for light has been a challenge, but a novel approach using time-dependent optical transitions in a nanoplasmonic waveguide has been proposed in this study. This configuration allows for strict one-way flow of light, with full reflection in one direction and undisturbed transmission in the other. This concept has potential applications in communications, smart windows, thermal radiation management, and solar energy harvesting.