LAUSR

Long-range, high-power wireless power transfer (WPT) and high-capacity communication can be achieved simultaneously in the resonant beam system (RBS), characterized with spatially separated transmitter and receiver. However, human safety in space transmission cannot be guaranteed if the transmitted power is above a certain level (e.g., several Watts). Thus, in this article, we propose a self-protection RBS, in which the protective beams embrace the energy-transfer resonant beam and are formed by the refracting part of the resonant beam emitted from the output reflector. If an external object comes across the protective beam whose power is very low, the protective beam transmission is cut off. Meanwhile, the resonant beam is interrupted due to the limit of excitation threshold. Then, we reveal the self-protection mechanism based on electromagnetic field propagation, self-mixing interference effect, and output power model. Afterward, we demonstrate that safe energy transfer can be realized by pumping gain medium with a pumping power that is greater than the threshold of the self-protection RBS and less than that of the unprotected RBS. Finally, the numerical results show that about 4.6-W electric power and 12.8 bps/Hz spectral efficiency can be transmitted at 2-m transmission distance safely in the self-protection RBS. Hence, the self-protection RBS provides a new way for safe simultaneous wireless information and power transfer (SWIPT) without mechanical control.