Charging a Smartphone Across a Room Using Lasers

We demonstrate a novel laser-based wireless power delivery system that can charge mobile devices such as smartphones across a room. The key challenges in achieving this are multi-fold: delivering greater than a watt of power across the room, minimizing the exposure of the resulting high-power lasers to human tissue, and finally ensuring that the design meets the form-factor requirements of a smartphone and requires minimal instrumentation to the environment. This paper presents a novel, and to the best of our knowledge, the first design, implementation and evaluation of an end-to-end power delivery system that satisfies all the above requirements. Our results show that we can deliver more than 2 W at ranges of 4.3 m and 12.2 m for a smartphone (25 cm2) and table-top form factor (100 cm2) receiver respectively. Further, extensive characterization of our safety system shows that we can turn off our laser source much before a human moving at a maximum speed of 44 m/s can even enter the high-power laser beam area.