If Solar Sails Work, THEN SO TOO WILL MY LIGHT CANNON

You're just jealous you didn't think of it first.

It's been done. But you need a small nuclear explosion to get enough photons to do anything useful. Focusing them is a bitch, too.

In the brief interval between fission trigger implosion and hydrogen bomb secondary ignition, a soft x-ray flow is diverted down the secondary's long axis to compress it as the central plutonium carrot is synchronously initiated through a depleted U-238 partition between the two stages. Declassified estimates of conditions in that interval estimate the viscosity of photon flow to exceed that of water - and perhaps molasses.

OTOH, a plebian multi-kilowatt CO2 laser will deliver an adequate point of sale argument without being a propulsive photon cannon.