A group of researchers has managed to transmit 400mW of light power at a distance of 30 meters using infrared laser light . At the moment, small sensors can be charged with this technology, but in the future, if it is developed, larger devices such as smartphones could be charged.
The technology used is technically known as distributed laser charging and is safe, as the laser goes into a low power mode when not in use. This particular type of laser technology has been able to go further than previous experiments using similar wireless energy transmission technologies.
“While most other approaches require the receiving device to be on a special charging cradle or to be stationary, distributed laser charging allows for self-alignment without tracking processes as long as the transmitter and receiver are in line-of-sight.” from the other,” says electrical engineer Jinyong Ha, from Sejong University (South Korea).
The light bouncing components that make up a laser cavity are often together in the same device. Here, however, they are separated into a transmitter and a receiver, that is, the laser cavity is formed in the intervening space as long as the transmitter and receiver are in view.
To carry out the experiment, the researchers installed an amplifying transmitter specially treated with a silvery-white metal called erbium 30 meters away from the receiver, which was equipped with a photovoltaic cell to convert the light signal into electrical energy.
The receiver is 10 square millimeters in size, making it small enough to fit into compact devices, such as motion or temperature sensors that could be charged wirelessly using this technology.
Thanks to this technology, in the future we could charge our mobile phone while we use it without having to use cables or plugs . But before this can happen, the system will have to be able to transmit a larger amount of energy.
Part of that process could involve upgrading the receiver’s photovoltaic cell so that it would be able to convert more laser light into electricity. Another possible solution to the problem could be that the system works with several receivers at the same time.
With a central wavelength of 1550 nanometers, the laser is in the safest part of the infrared spectrum and is safe for skin and eyes . Scientists made a number of adjustments to improve the efficiency of the system and ensure that as much energy as possible was transferred.
“In the receiver unit, we incorporated a spherical lens retroreflector to facilitate 360-degree transmitter-receiver alignment, which maximized the efficiency of energy transfer,” says Ha. “We found experimentally that the overall performance of the system depended on the index of refraction of the spherical lens, with an index of refraction of 2003 being the most effective.
This wireless technology needs further refinement but in the future it could be useful not only on a personal level, for the electronic objects of each one of us, but also for those industries in which the wiring is difficult to assemble or maintain .
It’s still early days for this technology, but wireless power transfer could not only be beneficial for personal electronics, it could also make a big difference in industrial environments where cabling is difficult to mount or maintain.
“Using laser charging to replace power cables in factories could save maintenance and replacement costs,” says Ha. “This could be especially useful in harsh environments where electrical connections may cause interference or pose a risk of fire”.
Referencia: Javed, N., Nguyen, N-L. et al. 2022. Long-range wireless optical power transfer system using an EDFA. Optics Express. DOI: https://doi.org/10.1364/OE.468766
