We first heard of them in Star Trek, photon torpedoes. We are on the verge of making them. It is simply a matter of storing a large number of photons and then releasing them suddenly.

Photons traveling through any substance slows down. We need only pump an hour's worth of light into one meter of a medium where the speed is say one meter per hour. At the end of the hour destroy the medium.

Of course it can work with less parameters. It depends upon how many photon can be put into the medium before they start coming out the other end. Also the medim can be bounded by mirrors so the light continues to pass back and forth through it.

A one megawatt laser produces one million joules per second. That could raise 1000 kilograms 1000 meter into the air. This would be overkill for most weapons applications.

Condensed matter is the candidate medium. It is destroyed by raising its temperature a fraction of a degree.

The best was to support the troops in time of war 
is to end the war and bring them home.
	-- The Iron Webmaster, 1819