Using diamonds to recharge civilian drones in flight

November 7, 2018, Ecole Polytechnique Federale de Lausanne
Credit: Ecole Polytechnique Federale de Lausanne

A small lab-grown diamond measuring a few millimeters per side could one day enable civilian drones to be recharged in mid-flight through a laser. Thanks to the diamond, the laser beam can remain strong enough over a long distance to recharge photovoltaic cells on the drones' surface. This system, which poses no threat to human health, is being developed by EPFL spin-off LakeDiamond. It could also be used to transmit both power and data to satellites and has just been included in the ten projects supported for two years by of the Swiss Space Office.

Drones are being used for a growing number of purposes. Their designs are ever more efficient, and techniques for flying them are being further refined all the time. But drones still have the same weak point: their battery. This is particularly true of propeller drones, which are popular for information-gathering purposes in dangerous or hard-to-reach regions. These drones can fly for only around 15 minutes at a time because their engines quickly burn through their batteries. One way of addressing this limitation – without weighing the drones down – would be to recharge them while aloft using a power beaming : an energy-rich that is guided by a tracking system and shines directly on on the drones' exterior.

Several labs around the world, including in the US, have been working on this idea in recent years. LakeDiamond, an EPFL spin-off based at Innovation Park, has now demonstrated the feasibility of using a high-power laser for this purpose. What's more, LakeDiamond's laser emits a wavelength that cannot damage human skin or eyes – the issue of safety is paramount, since the system is meant for use with civilian drones. LakeDiamond's technology is built around diamonds that are grown in the company's lab and subsequently etched at the atomic level.

World record for power

Despite appearances, standard laser beams are not as straight as they seem: as they travel, they expand ever so slightly, leading to a loss in density as they go. But LakeDiamond's system produces a laser beam with a wavelength of 1.5 µm that, in addition to being safe, can travel much farther without losing strength. "Systems developed by other companies and labs, often for military applications, employ lasers that are more powerful and thus more dangerous for humans," says Pascal Gallo, CEO of LakeDiamond. His company took the opposite tack: their technology transforms the rays emitted by a simple low-power diode into a high-quality laser beam. Their beam has a larger diameter, and its rays remain parallel over a longer distance – in this case up to several hundred meters.

In LakeDiamond's laser, the light produced by a diode is directed at a booster composed of reflective material, an and a small metal plate to absorb the heat. The breakthrough lies not with this set-up, which already exists, but with the fact that the emitted beam is only a few dozen watts strong. The secret is using a small square lab-grown diamond as the optical component, as this delivers unparalleled performance. LakeDiamond's system holds the for continuous operation using a wavelength in the middle of the infrared range – it delivers more than 30 watts in its base configuration. "That's equivalent to around 10,000 laser pointers," adds Gallo.

The lab-grown diamonds' key properties include high transparency and thermal conductivity. Achieving those things – and mastering the nano-etching process – took the researchers over ten years of development. LakeDiamond grows its diamonds through a process of chemical vapor deposition, an approach that ensures their purity and reproducibility. The surfaces of the resulting tiny square diamonds are then sculpted at the nano level using expertise developed in Niels Quack's lab at EPFL. Thanks to their inherent properties and etched shapes, the diamonds are able to transfer heat to a small metal plate that dissipates it, while at the same time reflecting light in such a way as to create a laser beam.

"To achieve greater power – say to recharge a larger drone – these lasers could easily be operated in series," says Nicolas Malpiece, who is in charge of power beaming at LakeDiamond. The company's remote recharging system works in the lab but will require further development and refinement before it's ready for field use. What would happen if a drone flies behind an obstacle and is cut off from its laser energy source? Several approaches to this problem are currently being explored. A small back-up battery could take over temporarily, or, for information-gathering missions over rough terrain for example, the could simply return to within range of the in order to top up its battery.

This energy transmission system is also interesting for other areas of application. It can for example be used for charging and transmitting data to satellites. The development of the system is included in a support program of the Swiss Space Office, which began on 1 November and runs for two years.

Explore further: Laser-powered-drones may beat endurance hurdles

More information: Carving diamonds for optical components: … -optical-components/

Related Stories

Laser-powered-drones may beat endurance hurdles

September 6, 2018

Hmm. Drones that can be recharged by a laser. So how long could they fly before having to land? How about "never mind"? We can look forward to seeing this idea in action. New Scientist had a story on September 3 that the ...

The Star Wars 'superlaser' may no longer be sci-fi

April 3, 2017

In a world-leading study researchers at Macquarie University have proven a method for multiplying laser power using diamond, demonstrating that a laser similar to the Star Wars 'superlaser' may no longer remain in science ...

Bit of bling adds new dimension to laser beam technology

December 11, 2008

( -- No longer just an expensive ornament, diamonds are now of a sufficient size and quality to attract the eye of a team of physicists at Macquarie University, who are using them to develop a new more powerful ...

New diamond laser 20 times more powerful

August 13, 2015

Researchers from the MQ Photonics Research Centre joined with fiber laser experts from the Fraunhofer Institute for Applied Optics and Precision Engineering in Jena, Germany to demonstrate a diamond laser 20 times more powerful ...

Recommended for you

Two new planets discovered using artificial intelligence

March 26, 2019

Astronomers at The University of Texas at Austin, in partnership with Google, have used artificial intelligence (AI) to uncover two more hidden planets in the Kepler space telescope archive. The technique shows promise for ...

Infertility's roots in DNA packaging

March 26, 2019

Pathological infertility is a condition affecting roughly 7 percent of human males, and among those afflicted, 10 to 15 percent are thought to have a genetic cause. However, pinpointing the precise genes responsible for the ...

Facebook is free, but should it count toward GDP anyway?

March 26, 2019

For several decades, gross domestic product (GDP), a sum of the value of purchased goods, has been a ubiquitous yardstick of economic activity. More recently, some observers have suggested that GDP falls short because it ...

Droughts could hit aging power plants hard

March 26, 2019

Older power plants with once-through cooling systems generate about a third of all U.S. electricity, but their future generating capacity will be undercut by droughts and rising water temperatures linked to climate change. ...


Adjust slider to filter visible comments by rank

Display comments: newest first

5 / 5 (2) Nov 07, 2018
Interesting. I really want to know where they are getting solar cells that will output enough amperage while mounted on the average drone to actually make charging the batteries worthwhile while the motors are pulling multiple amps of power. While I can see them extending the flight time a little bit, even a large drone doesn't have all that big a body for the cells to mount on to supply enough current to actually extend the time much. I guess that's why companies have been working on the idea for years? I can only see this idea working by making the drone super light with very little batteries (or maybe super caps) but with a large surface area for the solar cells. I read an article somewhere about how that had already been done. The problem is the drone had to be so light it could barely even carry a small ic camera and even a light breeze would make it uncontrollable. I wish the company luck though. Maybe they will figure out a way.
5 / 5 (2) Nov 07, 2018
@24volts: I imagine that the cells on the drone would be similar to cells used in concentrated solar applications? The drone would probably have some heat dissipation issues to deal with too.

Orientation of the cells could be a problem too. If they are mounted horizontally, along the underside of the body, then as the drone gets away from the laser location, the beam will be hitting the cells at an increasingly less perpendicular angle. It might be necessary to return closer to the laser to recharge. If they were suspended under the drone like a vertical fin, then the drone could charge at a distance, but would have to keep the cells aimed perpendicularly to the laser. This might not be too great aerodynamically if not just hovering or there's much wind. Or, maybe there could just be multiple lasers to deal with these issues.
not rated yet Nov 07, 2018
@ C_U - very perceptive comment!

Similar to CPV cells in several ways - able to handle high-intensity light, and stacked junctions in some cases.

Unlike sunlight, on a CPV cell, a laser is typically monochromatic, so stacking is not needed to get multiple band-gaps to efficiently handle multiple colors. However it still helps efficiency by raising voltage and reducing current and cutting resistive losses. The efficiency record for stacked cells converting laser light is getting close to 70%, if I remember correctly.

Yes, heat dissipation needs to be carefully managed, but high conversion efficiency helps quite a bit (less heat as well as more power).

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.