Well if you can propel something forward you can propel it backwards as well.

I'm assuming some sort of fixed laser type propulsion mechanism would leverage a type of solar sail technology. Maybe you could send a phased laser signal that "vibrates" a solar sail towards the source of energy instead of away.

> Well if you can propel something forward you can propel it backwards as well

Not necessarily - at least with currently known science. Light sails work ok transferring momentum from photons, allowing positive acceleration from a giant laser Earth. Return trip requires a giant laser on the other side.