Friday, September 18, 2009

Stanford Symposium: Extreme lasers for the next 50 years

If you think that laser performance is about maxed out, think of this. An extreme ultrafast laser as an alternative to particle accelerators. A high energy laser undergoing testing for initiating deuterium fusion. Optical tweezers that have unveiled the mechanical forces of kinesin, the protein that moves cargo within cells. And the brightest hard x-ray laser in the world, now up and running at SLAC. These were highlights from this year’s Stanford Photonics Research Center annual symposium, which also launched the first event of LaserFest, the official celebration of the 50th anniversary of the laser.

Gerard Mourou, from Europe’s ultrafast ELI project, led off by describing how we are entering a new era in high peak power lasers. The 1960s began the Coulombic epoch, where lasers could excite atoms to higher energy states, but still bound to the atoms. The 1990s saw the Relativistic epoch, where lasers can excite particles to relativistic levels. He said that we are about to enter the Nonlinear QED epoch, where lasers may examine the vacuum itself by scattering off of the virtual particles generated in the vacuum (which is essentially the “ether” of yore).

Such new lasers offer an alternative to giant particle accelerators. An accelerator uses a “momentum paradigm,” meaning that it imparts high momentum to particles and then observes them in a small volume. An extreme ultrafast laser operates in an “amplitude paradigm,” said Mourou. It is good for low mass particles, perhaps even dark energy, by observing them with low momentum in a larger volume.

At another extreme, the National Ignition Facility (NIF) at Livermore, California, will be the most energetic laser system in the world when it is fully operational. In fact, each of the parallel solid-state lasers of the facility is the largest in the world. All 198 of them are combined and focused to a target the size of a peppercorn inside a can the size of a pencil eraser. The overall system takes up a building that covers three football fields.

The NIF has three missions. One, to help understand the aging nuclear weapons arsenal. Second, to advance the study of fundamental physics. And third, it offers a path to clean fusion energy, with the aim of following up with a dedicated steady-state fusion reactor. Such a prototype reactor, and the many that might one day follow, would use oodles of diodes for pumping solid-state lasers, a potential killer app not lost on many diode suppliers (and one that I will comment on in a later blog piece).

A point that came out was the many years these grand projects can take to launch. In two of the projects here, it took 10 to 14 years to win funding, and another 4 to 10 years for construction. It adds up to 18 to 20 years from concept to completion.

Mourou noted that the laser has seen no boundaries, only horizons. If all goes well, these grand projects will do far more than just break performance records.

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