After being safely amplified to a higher energy level, the light can be compressed again by another grating. The end result: more powerful pulses and lossless amplifiers. This “chirped pulse amplification” has become a basic feature of high-power laser pointer. In 1996, it enabled researchers to use lasers to generate the world’s first PW-level pulses. Since then, LLNL has been pursuing higher energy levels to achieve laser-driven nuclear fusion.
In an effort to heat the miniature hydrogen capsules to the melting temperature, the laboratory’s national ignition device created pulses with a power of 1.8 MJ. However, these pulses are relatively long and still only produce 1PW of power. To control the nuclear process with strong light, scientists have turned to the time domain for high power: making the pulse energy last even shorter.
One method is to amplify the light in the titanium-doped sapphire crystal. Such crystals produce light with a broad spectrum. These pulses bounced back in a laser pointer chamber made up of a mirror. The individual frequency components cancel each other out for the duration of most pulses, but reinforce each other in short pulses that last only a few tens of femtoseconds. Providing a few hundred joules of energy to these pulses will yield a peak power of 10 PW.