Saw this on Larry Niven/Jerry Pournelle's novel, Footfall
So... big tank full of fuel & oxidant and someone's going to point a big laser at it...? Well, the video will be fun, at least. I like explosions. (/humour-off)
Seriously though, high-powered lasers are still off in the distance, the power requirements are huge and there's a lot of work to do before you can effectively shoot a laser up a rocket's bum while it's moving without going off-target and causing an oopsie.
My opinion, for what it's worth, is that by the time they get all the bits together to make this work, we'll have low-cost rockets and spaceplanes plus enough orbital infrastructure to make this method unneeded.
Now lasers and solar sails in deep space ala Robert Forward's Flight of the Dragonfly, now that's something I'd like to see...