XUV Comb Generation

Number 757 #1, December 7, 2005 by Phil Schewe and Ben Stein

The Top Physics Stories for 2005

At the Relativistic Heavy Ion Collider (RHIC) on Long Island, the four large detector groups agreed, for the first time, on a consensus interpretation of several year’s worth of high-energy ion collisions: the fireball made in these collisions -- a sort of stand-in for the primordial universe only a few microseconds after the big bang -- was not a gas of weakly interacting quarks and gluons as earlier expected, but something more like a liquid of strongly interacting quarks and gluons (PNU 728).

Physicists at JILA, the joint institute of NIST and the University of Colorado, have created a new optical process to extend the production of coherent radiation into the extreme ultraviolet region of the electromagnetic spectrum. This process takes advantage of the fact that ultrafast laser pulses of femtosecond widths, separated by nanoseconds, manifest themselves as a superposition of light at different frequencies over a wide spectral band. 

We've come a long way from the days when the length of the king's forearm was used to determine an object's size. Then, it was called the cubit, but the succession of short- and long-limbed kings made uniformity difficult. More modern standardized measures have helped. But these days, even those aren't enough. That's why the agency that sets measurement standards for the United States - the National Institute of Standards and Technology - is asking American technologists to assess the needs for new ones. With 80 percent of world trade dependent on such standards, NIST wants to be up to speed.

The world's most accurate "ruler" made with extreme ultraviolet light has been built and demonstrated with ultrafast laser pulses by scientists at JILA, a joint institute of the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder.