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Asked by andrewgwoods15 to Joel, Kristian, Tim, Venus, Zachary on 18 Nov 2013.
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Kristian Harder answered on 18 Nov 2013:
Actually, good question for me – when I leave my lab area, go down the corridor for a few steps, I end up right in front of the control room of one of the most powerful lasers on the planet. Maybe even *the* most powerful laser on the planet, but I am not sure about the numbers. The one at Rutherford Lab that I am talking about is called Vulcan, and it sends laser pulses of about 1 Peta-Watt power. That is about as much power as several hundred nuclear power stations can produce. BUT, there’s a catch. It only has that much power for an extremely short period of time. One pulse is only 500 femtoseconds long, which is 500 millionth of a billionth of a second. And then it needs to recharge for about ten minutes to send the next pulse. There is now a similarly powerful laser in the USA called BELLA, and that can give you a Peta-Watt pulse every second or so. That’s more like it. 🙂 I think these lasers work with extremely powerful flashlights around big sapphire crystals, prompting those crystals to send out a short laser pulse, which is then tweaked and shortened and focused.
These lasers are quite big. They pretty much need their own building.
You can do a lot of neat things with these lasers. Create plasma, study chemical reactions like in a stop motion movie, thanks to very high resolution high speed photography and much more.And just one more note, because this high power thanks to extremely short pulses for me doesn’t really say much about the “strength” of the laser, even though there are of course good reasons for people to develop lasers with such pulses. I think a much better measure of “strength” is the so-called brilliance, which is more or less a sustained beam intensity. And as far as that is concerned, it will be hard to beat a massive over 2 mile long laser currently under construction in Hamburg, the X-FEL, which is essentially a particle accelerator, bringing up an electron beam to enormous kinetic energy, and then turning some of that kinetic energy into X-ray laser output. *That* is what I call a laser. 🙂
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Tim Hollowood answered on 19 Nov 2013:
Hi, my colleague Kristian is in just the right place to answer this question. People are trying to see whether these incredibly could be used to create nuclear fusion in a controlled, that is the process in an atomic bomb. Theoretically if we could extract the energy of nuclear fusion we would have a virtually inexhaustible supply of clean fuel and that would be very very cool….well hot!
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Zachary Williamson answered on 21 Nov 2013:
Well I think Kristian’s covered the most powerful laser bit, since he works next to it!
As for how lasers are made. They’re created by energizing electrons in atoms. Electrons in atoms, because of their quantum mechanical nature, can only have a very limited number of energy states. When you energize one of these electrons by hitting it with light, it will only absorb a very specific, known quantity of energy (that amount of energy absorbed depends on the atom). Eventually, because this new energy state is unstable, the electron will emit some light and drop back down into its normal state. That light will have a fixed amount of energy, and therefore a fixed wavelength and colour.
We create lasers by exiting vast amounts of these electrons, which in turn emit vast amounts of light at exactly the same wavelength. The atom used changes the energy of the light and therefore its colour.
Incidentally, whilst this isn’t the most poweful application it’s probably the oddest: in the 1970s Soviet Russia developed a laser tank! http://en.wikipedia.org/wiki/1K17_Szhatie . Lasers back then weren’t powerful enough to use as weapons, its purpose was to use its laser to guide other ‘real’ tanks and enable them to accurately hit targets. Still pretty cool though.
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