Laser Makes Black Holes

Imagine being able to peek inside a black hole and even perform experiments there. It may not be as far-fetched as it sounds, thanks to a team that claims to have simulated a black hole’s event horizon in the lab.

Ulf Leonhardt at the University of St. Andrews, Scotland, and his colleagues accomplished the feat by firing lasers down an optical fiber, exploiting the fact that different wavelengths of light move at different speeds within the fiber.

They first shot a relatively slow-moving laser pulse through the fiber, then sent a faster “probe wave” chasing after it. The first pulse distorts the optical properties of the fiber simply by traveling through it. This distortion forces the speedy probe wave to slow down dramatically when it catches up with the slower pulse and tries to move through it. In fact, the probe wave becomes trapped and can never overtake the pulse’s leading edge, which effectively becomes a black-hole-event horizon, beyond which light cannot escape.

This “laser black hole” could allow physicists to examine what happens to light on both sides of a event horizon -- “a feat that is utterly impossible in astrophysics”, the researchers said in a university statement.

Cosmologists have already worked out exactly how light should change frequency as it approaches an event horizon -- from the outside or the inside of a black hole -- and sure enough, the team observed exactly these shifts in their experiment.

It should also be possible to use the artificial event horizon to help test whether anything can escape from a black hole, the university said. "In the 1970s, Stephen Hawking predicted that hot black holes could radiate particles, dubbed Hawking radiation, but it’s tough to check this using telescopes, because they’d be swamped by noise. The team calculates that their laser black hole shares this property, and that it will 'radiate' photons if it heats up to about 1000 degrees centigrade."

Ray Rivers at Imperial College London is impressed by the work’s potential to test astrophysical phenomena: “They’ve done some clever stuff to give us a chance of seeing Hawking radiation for the first time,” said Leonhardt, who presented the results at a Cosmology Meets Condensed Matter meeting held last month at the Royal Society in London.'

For more information, visit: www.st-andrews.ac.uk