Light Beams Can Create Lift

A team of researchers in New York was recently able to determine that light waves can create the same type of force as the one allowing airplanes to take of in the air. The group determined that specific types of light beams can be used to create enough lift to carry microscopic particles around.

The fact that light is able to push objects has been known for a long time. The entire concept of a solar sail, such as the Ikaros demonstrator launched by the Japanese Aerospace Exploration Agency (JAXA) earlier this year, revolves around the push of light.

So the fact that photons can instill motion in an object was known. What the new study showed was that the elementary particles making up light can also create much more complex forces.

The physics team, which was based at the Rochester Institute of Technology (RIT), discovered that an uniform stream of photons was able to create enough lift to move a microscopic particles up and down.

The new concept is called optical lift, and researchers still don't know whether it will have any practical applications. It's doubtful that full-size airplanes will be able to fly atop light beams, but several uses could be found in the electronics industry, and related fields.

For example, micromachines could use these light beams as a source of energy. Conversely, the focused light could be used to transport tiny particles from one place to another. Researchers say that it will also be possible to develop better control methods for solar sails.

University of Glasgow physicist Miles Padgett says that the new study holds some very interesting possibilities, but steers clear of declaring his enthusiasm for the discovery. “Maybe it’s useful, maybe it’s not. Time will tell,” he says.

“If we have something in the shape of a wing and we shine light through it, what happens?” this was the question expert Grover Swartzlander and his team asked before the study began.

In subsequent experiments, every time an asymmetrical deflection of light would be achieved, the beam would generate a highly-stable lift force, which completely surprised investigators at first.

The beams were directed initially at regular microscale particles, but then the RIT team decided to spice things up, and used tiny aerodynamic nanorods for the investigation.

They developed two setups, one in which the focused light was directed as microscopic spheres, and another in which the nanorods were the target. The latter particles were round at one end and flat at the other.

In the first group, light pushing from underneath made the particles travel towards the microscope, while in the second group, the additional lift force caused the nanorods to slide sideways.

“The subtlety is that it actually self-stabilizes. It twists a little bit one way, and you think, ‘Oh dear, it’ll stop working,’ then the light rotates it back again,” explains Padgett, quoted by Science News.