Charging A Smartphone Over the Air: The Resonant Beam Charging Method

TL;DR

This paper introduces a novel resonant beam charging system that enables wireless smartphone charging over several meters without tracking control, demonstrating practical power transfer with minimal diffraction loss during mobility.

Contribution

The study presents a self-aligned resonant beam charging method using optical resonators and retroreflectors, eliminating the need for tracking control in long-distance mobile power transfer.

Findings

Achieved over 5 W optical power transfer with 0.6 W electrical power output.

Demonstrated effective charging within 2 meters vertically and 18 cm horizontally.

System enables mobile smartphone charging with negligible diffraction loss.

Abstract

Wireless charging for mobile Internet of Things (IoT) devices such as smartphones is extremely difficult. To reduce energy dissipation during wireless transmission in mobile scenarios, laser or narrow radio beams with sophisticated tracking control are typically required. However, reaching the necessary tracking accuracy and reliability is really difficult. In this paper, inspired by the features of optical resonators and retroreflectors, we develop an experiment on a self-aligned resonant beam charging system for long-distance mobile power transfer. It exploits light resonances inside a double-retroreflector-based spatially separated laser resonator (SSLR), which eliminates the requirement for any kind of tracking control. Focal telecentric cat's eye retroreflectors are employed here. The SSLR was investigated by both theoretical calculation and experiment. We also well assembled the transmitter and the receiver and demonstrated its application in mobile smartphone charging. The results show that above 5-W optical power (also obtained more than 0.6-W electrical power) transferring with negligible diffraction loss to a few-centimeter-size receiver is realized while the receiver moves arbitrarily within 2-m vertical distance and 6{\deg} field of view from the transmitter. The maximum horizontal moving range is up to 18cm. This wireless charging system empowers a smartphone in mobile operation with unlimited battery life without the need for a cable.