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Physics/Megaton level lasers

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Question
Hi! In some science fiction stories there are laser weapons which can release energy per shot equivalent to megatons of tnt. So wouldn't basically channelling energy equivalent of megatons of tnt in one shot of the laser overheat and melt the components of the laser? And how much energy can a laser usually withstand being channeled through it without melting?

Answer
Your first basic question should be answered with a 'probably' - but we don't have anything remotely like that.  For lasers of any sort, the thing to consider is power per pulse divided by pulse duration.  So there is average power, and then there is max power during the pulse.  While the power during a focused laser pulse can easily be in the megawatts if the pulse is short enough, the total energy in such a pulse is pretty low.   

Your second question is not appropriate as melting is not how lasers fail, at least when too much power is applied.  You don't melt your laser -  other things start to be a problem well before that.  Specifically, most laser materials (gas, dyes, crystals) have a max power density.  Once you get to that, the laser starts to 'leak' light. While some heat build up can happen if your system is not put together well, this is not usually a problem.

Here are three state of the art high powered laser systems for you to check out if you have an interest in seeing what we can currently accomplish.

Record Breaking Pulsed Laser
http://cuos.engin.umich.edu/researchgroups/hfs/facilities/hercules-petawatt-lase
Most Powerful Uranium Enrichment Laser
https://lasers.llnl.gov/science/icf
Best field tested laser weapon to date
http://news.yahoo.com/blogs/sideshow/how-the-army-s-recent-successful-laser-test

I hope this helps!

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Dr. Jeffery Raymond

Expertise

Materials chemistry. Materials science. Spectroscopy. Polymer science. Physical Chemistry. General Physics. Technical writing. General Applied Mathematics. Nanomaterials. Optoelectronic Behavior. Science Policy.

Experience

Teaching: General Inorganic Chemistry I & II, Organic Chemistry I & II, Physical Chemistry I, Polymeric Materials, General Physics I, Calculus I & II
My prior experience includes the United States Army and three years as a development chemist in industry. Currently I am the Assistant Director of the Laboratory for Synthetic Biological Interactions. All told, 13 years of experience in research, development and science education.

Organizations
Texas A&M University, American Chemical Society, POLY-ACS, SPIE

Publications
Journal of the American Chemical Society, Nanoletters, Journal of Physical Chemistry C, Journal of Physical Chemistry Letters, Ultramicroscopy Proceedings of SPIE, Proceedings of MRS, Polymer News, Chemical and Engineering News, Nano Letters, Small, Chemistry.org, Angewandte

Education/Credentials
PhD Macromolecular Science and Engineering (Photophysics/Nanomaterials Concentration), MS Materials Science, BS Chemistry and Physics, Graduate Certificate in Science Policy, AAS Chemical Technology, AAS Engineering Technology

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