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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.”
It only lasted for a picosecond...
Longer than I usually do.
It only lasted for a picosecond...
A petawatt for a picosecond is one kilojoule. That is enough energy to warm a liter of water by 0.24C.
Help me understand. Is a two petawatt laser being fired for a picosecond more like being sneezed on by a rhino with a cold or more like being shat on by an elephant with a bad case of explosive diarrhea?
Why should anyone care about the power level, as opposed to the pulse energy?
people who have tattoos should care, for one. the ideal tattoo removal laser has really high instantaneous power but really short pulses. this way you get high power but low energy per pulse.
the tattoo ink breaks down better with higher power lasers because it breaks the bonds holding the ink molecules together. but by keeping the energy per pulse low, you're minimizing the tissue damage since tissue damage grows with the amount of energy absorbed by the skin. when you break up the ink molecules into smaller pieces then the immune system can flush away the bits into your lymph nodes. tattoo is gone!
I'd get fired too
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.
I don't know about those times scales, but femto-second pulsed lasers are damn useful for imaging. Briefly, say the experimenter images green fluorescence. Normally, to get green fluorescence you need to excite with blue light of, say, 450 nm. However, if you can pack enough photons into a short packet then you can also get green fluorescence at about double the wavelength. It's called "two photon absorption" and won a Nobel prize. So you pump in 900 nm light and get back green. The advantage is that longer wavelengths are scattered less by biological tissue and, crucially, the depth of field is much better so there is very little out of focus emitted green light (see image in link). Because the laser scans over the specimen relatively slowly (e.g. a few times a second), you can collect scattered green photons and still assign them back to where they came from. So it's very efficient. Maybe this new laser will all for the process to work efficiently with 3 or even 4 photons.
soylentnews.org
It only lasted for a picosecond...
They couldn't risk cooking the shark it was attached to.