You can use your existing 3D printing software!
- Make a new profile for your favorite software (Skeinforge, slic3r, Cura and so on).
- This profile should have Z scaling set to -1, so that the Z axis will move UPWARD as the cut proceeds.
- Layer height and filament size should be 0.05mm (roughly the effective beam width).
- Infill should be set to zero percent.
- Travel speed should be set as high as possible within your printer’s capability; 3000mm/sec is a good starting point.
- Flow rate should be set to zero.
- Feed rate is used to control cutting; some values for materials follow. — Paper: 12mm/sec — Acrylic: 2mm/sec — Leather: 5mm/sec
- An «engraving» profile can be done by setting the slicer to only process the first layer.
- The profile should have appropriate start and end gcode. The M400 command is your friend here!
Draw the object in Sketchup and then use the «push» command to raise it to the height you want, then export to STL and slice normally. Be sure that your start/end gcode sets the Z axis to the proper focal length!