Cleaning boreholes formed by millimeter wave drilling

A system comprising:

• an electromagnetic wave emitter configured to emit an electromagnetic wave, the electromagnetic wave emitter located at a topside facility;
• a surface waveguide system configured to direct the electromagnetic wave into a workstring;
• the workstring extending from the topside facility and into a borehole;
• and
• a bottomhole assembly at a downhole end of the workstring, the bottomhole assembly comprising:
• a body defining a passage therethrough defining a waveguide for an electromagnetic wave, the body comprising:
• a uphole end configured to be coupled to a workstring further defining the passage extending uphole to a topside facility;
• and
• a downhole end comprising an outlet of the passage, the downhole end comprising an emitter configured to emit the electromagnetic wave;
• and
• a reamer extending from the body, the reamer configured to scrape slag, produced by electromagnetic wave drilling, from a wall of a wellbore.