Weighing in at a mere 20 billion trillion watts per square
centimeter and containing a measly 300 terawatts of power, the
University of Michigan has broken a record with a 1.3-micron speck wide
laser. It’s about two orders of magnitude higher than any other laser
in the world and can perform for 30 femtoseconds once every ten seconds
— some of the researchers speculate it is the most powerful laser in the universe.

If you could hold a giant magnifying glass in space and focus all the
sunlight shining toward Earth onto one grain of sand, that concentrated
ray would approach the intensity of a new laser beam made in a
University of Michigan laboratory.

"That’s the instantaneous
intensity we can produce," said Karl Krushelnick, a physics and
engineering professor. "I don’t know of another place in the universe
that would have this intensity of light. We believe this is a record."

The pulsed laser beam lasts just 30 femtoseconds. A femtosecond is a millionth of a billionth of a second.

Such intense beams could help scientists develop better proton and
electron beams for radiation treatment of cancer, among other
applications.

The record-setting beam measures 20 billion trillion watts per
square centimeter. It contains 300 terawatts of power. That’s 300 times
the capacity of the entire U.S. electricity grid. The laser beam’s
power is concentrated to a 1.3-micron speck about 100th the diameter of
a human hair. A human hair is about 100 microns wide.

This intensity is about two orders of magnitude higher than any
other laser in the world can produce, said Victor Yanovsky, a research
scientist in the U-M Department of Electrical Engineering and Computer
Science who built the ultra-high power system over the past six years.

The laser can produce this intense beam once every 10 seconds, whereas other powerful lasers can take an hour to recharge.

"We can get such high power by putting a moderate amount of energy
into a very, very short time period," Yanovsky said. "We’re storing
energy and releasing it in a microscopic fraction of a second."

To achieve this beam, the research team added another amplifier to
the HERCULES laser system, which previously operated at 50 terawatts.

HERCULES is a titanium-sapphire laser that takes up several rooms
at U-M’s Center for Ultrafast Optical Science. Light fed into it
bounces like a pinball off a series of mirrors and other optical
elements. It gets stretched, energized, squeezed and focused along the
way.

HERCULES uses the technique of
chirped pulse amplification developed by U-M engineering professor
emeritus Gerard Mourou in the 1980s. Chirped pulse amplification relies
on grooved surfaces called diffraction gratings to stretch a very short
duration laser pulse so that it lasts 50,000 times longer. This
stretched pulse can then be amplified to much higher energy without
damaging the optics in its path. After the beam is amplified to a
higher energy by passing through titanium-sapphire crystals, an optical
compressor reverses the stretching, squeezing the laser pulse until
it’s close to its original duration. The beam is then focused to
ultra-high intensity.

In addition to medical uses, intense laser beams like these could
help researchers explore new frontiers in science. At even more extreme
intensities, laser beams could potentially "boil the vacuum," which
scientists theorize would generate matter by merely focusing light into
empty space. Some scientists also see applications in inertial
confinement fusion research, coaxing low-mass atoms to join together
into heavier ones and release energy in the process.

A paper on this research, "Ultra-high intensity 300-TW laser at 0.1 Hz repetition rate," is published online in the journal Optics Express. The full text is available at http://www.opticsinfobase.org/abstract.cfm?URI=oe-16-3-2109. Yanovsky and Krushelnick are authors of the paper.

Via Physorg