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Japanese Scientists Fire the Most Powerful Laser On the Planet
Sepa Blackforesta writes: Scientist from University of Osaka claim have fired the world's most powerful laser. The beam was intact for 2-petawatt, pulse lasted just one picosecond. While it produced a huge amount of power, the energy required for the beam itself is equivalent to that needed to power a microwave for two seconds. An associate professor of electrical engineering at Osaka University Junji Kawanaka says “With heated competition in the world to improve the performance of lasers, our goal now is to increase our output to 10 petawatts.”
Timewise, atomic/molecular physics spans many orders of magnitude (from metastable states with lifetimes measured in hours, to inner-shell Auger processes with lifetimes measured in femtoseconds).
However making short pulses isn't the true goal of lasers like this (A Q-switched laser that fits on a coffee table can make femtosecond pulses). The true thing of interest is the *number density of photons*. Since it's a laser, the photons have the same energy. Then the total number of photons is proportional to the energy in the pulse, but the *number density* - N/V - scales as the inverse of the spot size and the inverse of the duration (since duration = length / c).
Therefore, the smaller the spot size and the shorter the pulse, the higher the number density of photons that is acheived in a given energy.
When you have a high enough number density, nonlinear things (whose rate of occurrence is the number density of photons raised to the order of the nonlinearity) happen and nonlinear things are Generally Interesting. For example, a sufficiently high laser power is capable of literally blowing protons/neutrons out of an atomic nucleus - IF you can dump roughly a nucleon binding energy into an area the size of a nucleus, in less than the time it will try to radiate it away.