Gyrotron isn't quite a maser, more akin to a free-electron (i.e. electron beam) RF source. AFAIR (might be wrong, but based on what I could find there: https://www.thinkgeoenergy.com/wp-content/uploads/2021/03/mi...) they aren't literally vaporizing the rock, rather locally heating it til it crushes into particles that can be blown away.