Lasers on a platter

After radios, tape recorders 'and TV's the Japanese are now working to reduce the size of high-power lasers

Published: Monday 15 April 1996

-- THE nation that makes radios the size of credit cards and tape recorders small enpu~ to slip into shirt pockets, has set its sights on a new target for miniaturisation. This time, however, the customers will be physicists and other researchers. And thego~l is any- thing but small: to squeeze the capabili- ties o(hi~ power lasers, devices that fill warehouse-sized buildings and pack many times the power o(the entire us electrical grid, into a new generation of lasers that can fit on a table top.

The task will fall, according to a report (Science, Vo127) on the Japan Atomic Energy Research Institute (JAERr), which announced last October that it plans to spend between us $80 million and $100 million a year over the next five years to set up the Advanced Photon Research Centre in Keihanna Science City outside Osaka.

The Centre's goal is to vastly extend the abilities of current short-pulse lasers, which achieve cstaggering power levels by packing all oftheir out- put into a pulse lasting a tiny fraction of a second. If it succeeds, the Centre will go on to turn these lasers into neW tools for accelerating particles, creating holo- graphic x-ray images of living cells, and exploring ultra-high speed phenomena by using rapidfire laser pulses as strobes.

"Our philosophy is to concentrate on table-top science," says Masashi lizumi, director general of JAERr'S efforts in both syn- chrotron radiation and photon research, The JAERI programme aims to build on recent advances in high-power, compact lasers.

These short pulses turn out just mil- lijoules of energy, but because the pulse is focused down to a spot just a few micrometers wide and lasts just tens of femto seconds ( quadrillionth of one second), they can achieve intensities greater than those of the largest existing lasers, such as the us $175-million Nova laser at Lawarence Livermore National Laboratory in California.

The Livermore system is referred to as 'a dinosaur' for the type of research Japan wants to do. There are already table top systems that can reach peak powers in the range of 100 terawatts, a development that has opened new strategies for accelerating particles and generating x-ray laser beams.

JAERI'S initial goal, for AD 2000, is to maintain a pulse of 30 femtoseconds or less, while increasing peak power by an order of magnitude to a petawatt { 1015 watts), or 1000 terawatts. In addition, scientists hope to speed up by two orders of magnitude the rate at which pulses can be generated from present levels of 10 to 20 hertz. No one else in theshort-pulse laser field is mentioning such numbers.

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