Infrared Laser Wireless Power System Delivers Usable Energy From Around 100 Feet Away

Using a ball-shaped retroreflector and a solar cell, a team from Sejong University has powered an LED over a 100-foot distance.

A team of researchers from Korea's Sejong University has shown off a method for delivering useful amounts of power wirelessly over a long range — using infrared lasers to push power to gadgets up to 100 feet away.

"The ability to power devices wirelessly could eliminate the need to carry around power cables for our phones or tablets," claims research team lead Jinyong Ha of the problems the work could solve. "It could also power various sensors such as those in Internet of Things (IoT) devices and sensors used for monitoring processes in manufacturing plants."

Wireless power transmission isn't anything new, but most systems rely on either inductive coupling or short-range radio signals between objects close enough to touch. What Ha and colleagues have created, though, uses infrared laser light — and delivers its power over distances up to 100 feet.

"While most other approaches require the receiving device to be in a special charging cradle or to be stationary, distributed laser charging enables self-alignment without tracking processes as long as the transmitter and receiver are in the line of sight of each other," Ha explains. "It also automatically shifts to a safe low power delivery mode if an object or a person blocks the line of sight."

The team's prototype uses a 1,550nm laser — running at a low enough power that it is not dangerous to the human eye — with a narrowband beam transmitting power to a receiver with a spherical ball-lens retroreflector for 360-degree coverage. When the laser hits the retroreflector in the receiver, which measures just 0.4" on a side, it is bounced to a photovoltaic cell to generate electricity to power an LED.

In testing, the system proved able to transmit 400mW of power over a 30 meter (around 100 feet) distance, though inefficiencies on the photovoltaic side reduced this to a usable electrical power of 85mW — enough to run the LED, and potentially to drive low-power sensor systems too.

The team has plans for boosting the output considerably, however: "Using the laser charging system to replace power cords in factories could save on maintenance and replacement costs," predicts Ha. "This could be particularly useful in harsh environments where electrical connections can cause interference or pose a fire hazard."

The team's work has been published in the journal Optics Express under open-access terms.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire:
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