Relative to planet #9 we're right next to a giant nuclear fusion powered light 700,000 km across. If it isn't lighting up the surface of planet #9 well enough for us to see it already, then we're not going to be able to construct some laser that makes a difference.
That's before you get to the problem that space is ridiculously big, and sweeping it across the entirety of the surface of the imaginary sphere that might contain planet #9 would probably take millions of years (citation needed).
That's before you get to the problem that space is ridiculously big, and sweeping it across the entirety of the surface of the imaginary sphere that might contain planet #9 would probably take millions of years (citation needed).