Live Science has a brief but interesting discussion of the plausibility and practicality of laser guns, one of the biggest SF tropes.  Short version:  We are likely to see some energy weapons, but they won’t use visible light and they won’t look anything like the light pulses in films like Star Wars. There also won’t be hand-held energy weapons anytime soon.

“For strategic and tactical weapons, you can store energy on planes, boats or Humvees,” said Beason, “but unless a super-source of energy is invented, you may never be able to do it with handheld weapons.”

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The reason a visible light beam shows up is that particles along its path scatter photons into the eyes of an observer. (Think of a flashlight beam in fog versus the same beam on a clear night.) “Anytime you can see a beam, that means light is being scattered in some way,” said Beason. That, in turn, means less energy reaching the target.

Though I don’t spend a lot of time thinking about it, I can see them existing most often in space where there isn’t an atmosphere to diffuse the light, and where discharging a projectile would have more challenges (no atmospheric oxygen to make a bang and the kickback pushing your ship in the other direction).  It will be quite awhile before we see any of this, if ever.