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.