If you forgot your charger today, engineers from the University of Washington have a solution for you — and it’s lasers.

The researchers’ technology enables a laser emitter’s narrow, invisible beam to power up a smartphone from across the room — perhaps as quickly as a standard USB cable.

The team reported their findings in a paper published in the December online journal: Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable & Ubiquitous Technologies.

The University of Washington technology has two components: 1) a transmitter with a power-providing laser source, and 2) and a solar cell that mounts on the back of a phone, converting the laser power to electrical energy to charge the phone.

In comparison to some smartphones’ built-in near-field charging capabilities, which are limited to ranges of a few centimeters, the researchers say their system offers equivalent power. The team’s beam sends a steady 2W of power to a 15-square-inch area from a 4.3 meter — or about 14 feet — range.

The smartphone signals its location by emitting high-frequency acoustic “chirps” — sensitive enough for the laser emitter to pick up, but inaudible to our own ears.

“The beam delivers charge as quickly as plugging in your smartphone to a USB port,” said co- lead author Elyas Bayati, a UW doctoral student in electrical engineering. “But instead of plugging your phone in, you simply place it on a table.”

The emitter detects the smartphone on the desired charging surface — a table, for example — and activates the laser to begin charging the battery.

Will the laser system become a viable charging option?

Tech Briefs spoke with fellow author Vikram Iyer, a UW doctoral student in electrical engineering, about the technology’s potentially powerful possibilities.

Tech Briefs: What is most exciting to you about this system?

Iyer: We can actually transfer enough power to charge a phone at ranges like across a room. This, of course, raises the issue of safety, though, to make sure that humans aren't harmed by the high-power beam. So, on top of actually demonstrating wireless power transfer at these ranges, our key innovation is a safety system that turns off the laser before it can harm a human.

Tech Briefs: What safety mechanisms are in place?

Iyer: At the transmitter, the high-power laser, which we actually use for charging the phone, is surrounded by lower-power lasers. At a high level we use these low-power lasers to detect a human approaching the laser, and immediately turn it off before harmful exposure. To prevent damage to the phone, our receiver also integrates a heatsink to make sure it doesn't heat up too much.

The wireless charging system created by University of Washington engineers. The charging laser and guard lasers are normally invisible to the human eye, but red beams have been inserted in place of the guard beams for demonstration purposes. (Image Credit: Mark Stone/University of Washington)

Tech Briefs: What was the inspiration for the wireless-charging idea?

Iyer: Our lab has explored harvesting power from Wi-Fi and other methods before, which is great for small, low-power sensors, but orders of magnitude less than you need to do things like charge phones. The fundamental problem, though, is that sending that much power over the air can be harmful to a human within that path. We realized that by choosing a laser, we can make sure the harmful energy is concentrated in a narrow, focused beam. We instead focused on designing a safety system that detects approaching human motion and turns off the laser before it can harm a person.

Tech Briefs: How do you envision this technology being used? Is it a viable charging option?

Iyer: We demonstrate phone charging at long range because it's something that other technologies can't do. We could make this a viable charging option for current phones as our receiver is small enough to integrate into a phone case.

Tech Briefs: What other applications are possible?

Iyer: A few we explore in the paper are using the system to power wireless cameras or other home automation devices mounted somewhere far from a power outlet, or to a table that could charge multiple devices. These are just a few examples; the basic ideas we demonstrate can be scaled to a variety of different applications for home use or even industrial applications that require wireless power.

What do you think? Will lasers offer a viable charging option? Share your thoughts below.