Engraving on Stained and polyurethane top coat

[LekoBrankovichpi]

I am brand new to the laser engraving hobby and would like to get comments on engraving with a 60W CO2 laser on finnished wood. When I say finnished wood, I mean stained and polyurethane top coated wood. I am trying to figure out my process and would prefer to laser on finnished wood if possible, but dont know if this will create problems or not.

Thanks, Craig