A newly created laser beam has a bit of a twist. Scientists have constructed a new time of laser that can actually form in a spiral.
The researchers first came up with the idea for a spiral laser by looking at angular momentum. While producing light with a controlled spin in a laser has been able to be done for decades, creating orbital angular momentum (OAM) beams inside a laser hasn't been able to be accomplished.
"We are all familiar with angular momentum in our everyday lives: the spinning Earth carries spin angular momentum while the orbiting Earth carries orbital angular momentum (OAM)," Andrew Robes of the University of the Witwatersrand, said. "Light can also carry angular momentum: through its polarization (spin), and through its pattern and phase OAM."
Light carrying OAM is actually created by twisting the phase of light into a spiral shape. The twisting light pattern, though, becomes tighter and tighter as you move to the center of the beam. This means that eventually the light disappears. Unfortunately, lasers usually can't tell the difference between clockwise and counter-clockwise. This means that the laser usually gives a combination of both in an uncontrolled manner.
"Our novelty was to realize that by using custom-geometric phase optics to map polarization to OAM, the laser could be designed to tell the difference between the clockwise and anticlockwise light," Forbes said.
So what exactly did the researchers do? They rotated a single optical element inside the laser, without any need for realignment. These types of beams have been used in optical communication. Now, a single laser can be created as well.
More interesting is the fact that the same laser can actually produce any combination of OAM beams and various polarizations of light. In the end, it could create arbitrary vector vortex beams.
"You have to understand that vector laser beams have proven immensely useful in machining metals and other materials with lasers, for example, in the automotive industry," Darryl Naidoo of the Council for Scientific and Industrial Research, said. "But until now we have not been able to produce all of them in one laser."
The findings are published in the journal Nature Photonics.
