Task one. Get ready to translate first four passages and to give a summary of the text. Self-bending light boomerangs could help surgeons

27 April 2012 by Justin Mullins

SELF-BENDING light beams capable of turning a corner like a boomerang are darting around an optics laboratory in France. The beams are just a few micrometres across, and could improve the way in which materials are carved on the microscopic scale, or help surgeons make curving incisions in the body that dodge specific regions or tissues.

Light normally travels in straight lines, but physicists have known for several years that superimposing a pattern on a laser beam can make it bend. The pattern is designed so that the individual light rays that make up the beam interfere with each other in a way that makes the beam curve.

However, a beam cannot normally bend by more than about 10 degrees without distorting. "The beam just doesn't keep its shape," says Mordechai Segev, at the Technion-Israel Institute of Technology in Haifa.

He and his colleagues took a deeper look at the problem by studying Maxwell's equations, fundamental laws covering the behaviour of electromagnetic waves. They calculated that it should be possible to make patterns that bend light beams by up to 180 degrees - an optical boomerang - without distorting them. The result is purely theoretical.

Unknown to them, however, a team led by John Dudley at the University of Franche-Comté in Besançon, France, had been taking a practical approach to the same problem. Dudley's team began experimenting with bending beams and found that they could go beyond the 10-degree limit. "This gave us the idea that we could achieve much greater curves," says Dudley's colleague François Courvoisier.

The team have bent beams just a few micrometres across by up to 60 degrees, using a device known as a spatial light modulator to superimpose the interference patterns. Dudley's team has already used these bendy lasers to carve glass into curved shapes. That could be useful as a rapid prototyping technique to test new designs of small optical features such as the tiny microlenses found in some cameras and projectors. "It allows you to test an idea quickly before going to full production," says Dudley. Surgeons might use curved beams to make surgical incisions behind structures inside the body.

incision - надрез, насечка, разрез dodge - избегать, увертываться, уклоняться

TASK TWO. Discuss the given abstract.

Setting the time on a clock is easy – unless it's one of the most accurate in the world. Now a light signal sent between two German cities has set a new record for the transmission of an atomic clock's tick. The feat, involving an optical fibre more than 900 kilometres long, could pave the way for a global network of synchronised, ultra-accurate clocks capable of testing fundamental physics.

Atomic clocks use precisely tuned electromagnetic waves to track the incredibly regular vibrations of atoms. Older atomic clocks tracked atoms that vibrate at microwave frequencies, while the latest generation use even faster optical frequencies. But while microwave clocks can be synchronised using satellite transmissions, these signals are too noisy for the more precise optical clocks