Infrared laser charger wirelessly beams power to devices 100 ft away

2022-08-30

We’re all used to receiving data wirelessly, but transmitting power over the air has been much trickier. Now Korean engineers have demonstrated a new system that uses infrared lasers to beam power as far as 100 ft (30 m), which could eventually lead to technology that automatically charges your phone as soon as you walk into a room.

Wireless charging is already a feature on current phones and other devices, but it’s functionally not much better than just plugging in a cord. The device usually needs to sit in a dock or make contact with a special surface, and can’t be moved far while charging.

For wireless charging to be really useful it would need to work over longer distances, sending power as seamlessly as Wi-Fi sends data. Scientists are working on that goal, experimenting with transmitting microwaves or lasers to devices, or generating electromagnetic fields that fill a room, but it often requires bulky and complex equipment.

For the new study, scientists at Sejong University developed a new wireless charging system that uses infrared light over a decent distance. It’s made up of two main parts – a transmitter that can be set up in a room, and a receiver that could be incorporated into electronic devices. The transmitter is an optical power source that uses an erbium-doped fiber amplifier, which produces a beam of infrared light with a central wavelength of 1,550 nanometers (nm).

This beam is then fired through the air to hit the receiver, which is made up of a spherical lens retroreflector. This focuses the incoming light into a point in the center, where there’s a photovoltaic cell waiting to absorb the light and produce electricity. If the line-of-sight between transmitter and receiver is broken, the device quickly and automatically switches to a low-intensity safe mode.

In tests, the team was able to transmit a 400-mW beam of light over a distance of 100 ft, where the 10 x 10-mm (0.4-in) receiver converted it into 85 mW of electrical power. That’s not a whole lot of energy – maybe enough to power a small sensor or two – but the team says that it could be scaled up to the point of charging everyday electronics like phones. Systems that work on a similar principle are being tested on more of a grid scale, to replace power lines.

The design has a few other advantages over previous wireless power systems. For one it doesn’t require a full-room renovation like some. The receiver’s ball shape lets it pick up incoming beams from any direction, meaning the transmitter doesn’t need to lock on or track the receiver, which is the case in things like Xiami’s Mi Air Charge system. It also works over much longer distances than devices like Duke University’s wall-mounted panels.

The team is currently working on improving the efficiency of the photovoltaic cell to boost the electrical output, as well as finding ways to charge multiple devices at once.

The research was published in the journal Optics Express.

New Atlas, 30 August 2022
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