Clean room assembly of laser disk amplifier

© LULI

Lasting only a thousandth of a billionth of a second, a burst of light hits a target. At one petawatt (10¹⁵ watts or 200 times that of the world's total electric power generation capacity), the pulse concentrates so much energy on its 10-micron-diameter target that matter is compressed to the point where thermonuclear fusion reactions are set off, replicating the conditions that obtain at the center of the Sun.

This fictional account will soon be a reality as 2003 saw the start of operations of Luli2000, slated to be progressively powered up until it reaches a petawatt in 2006. At this point the laser will be capable of delivering bursts of about a half kilojoule (kJ) for a duration of 500 femto-seconds. LULI's director³ is pleased; Luli2000 will help keep his laboratory at the forefront of intense laser research. LULI is in fact the most important center in France for intense high-energy lasers and acts as proving ground for the megajoule laser program of France's Atomic Energy Commission (CEA).

Another source of pride for the laboratory is Lucia, a 100 joules laser soon capable of 10 bursts per second, compared to the 20 minutes researchers are currently obliged to wait between firings! LULI and the Applied Optics Laboratory (LOA)⁴ are both part of this Ecole Polytechnique project, which is due for completion in five years.

In the meantime LULI users have at their disposal a two-beam kilojoule nanosecond-pulse laser facility (the first stage of the Luli2000 project), which replaces the former six-beam 100 joules setup, as well as a femtosecond laser of 100 terawatts.

With the new laser facilities scientists will be able to explore new research avenues, such as a new approach to fusion based on the concept of fast ignition: nanosecond lasers compress matter to up to 100 times its initial density, at which point femtosecond pulses pass through the plasma, generating at one point ten million degrees of temperature and triggering a fusion reaction.

Many other experimental uses of the new facility have been prepared as scientists from every field seek to test their ideas under the extreme and unique conditions generated by LULI's powerful tools. Not only plasmas but also gamma and X rays are being studied here, as well as accelerated particle beams generated by sending intense lasers through various targets, by which nanometric objects can by X-rayed. Astrophysicians are lining up to simulate supernovas, while geophysicists can use LULI facilities to reproduce the millions of bars of pressure characteristic of planets' cores.

For Arnold Migus, former director³ of LULI, such experiments are truly collaborative projects, as users work with LULI scientists to define their objectives. Categorised as a large national facility, LULI is by definition open to all French users (13 laboratories are involved) but also to European ones (more than a hundred European researchers have done work here). Programme committees share out available "laser time" among various projects. "We need to keep improving our facilities, or else researchers will turn to other laboratories such as the Rutherford Appleton Laboratory in England."

Competition between the two laboratories leads also to collaboration, as LULI, the RAL, and the GSI⁵ in Darmstadt have come together in a CNRS European Associated Laboratory (LEA)*. LULI has also been named by the CNRS to coordinate the Network for the Spread of Femtosecond Technologies (LASUR) and participates in the regional research and R&D net Optics Valley. As Migus³ points out, "LULI is a major nodal point in a research field that functions more and more in network mode."