if lasers produce so much power why can't we use it as an energy source
Well to get a laser beam you have to supply energy right? If laser is used as an energy source you are getting nothing but the same energy you had supplied, practically lesser perhaps...
Here are schematics of three laser devices; red laser pointer, green laser pointer and a Helium–neon laser. Where are the energy sources (power supplies) in the pictures?
some can produce terawatts of power so where do they get all that energy to feed into the laser
Power is not energy. Terawatt lasers produce very short pulses.
As others have pointed out, lasers are not a source of energy. The consume more energy than what comes out in the form of light.
The pulses are very short (short duration), which means high power (power = energy/time, see Power).
MPA-XL Femtosecond Terawatt Ti:sapphire Laser System ([STRIKE]see p.3 for system specifications[/STRIKE])
The Art of Amplification: A Desktop-Size 10 Terawatt Laser (ScienceDaily)
Edit: I replaced and striked out a link to a pdf document which did not work.
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