Design Cleaner tidies up the structural clutter that synthesis tends to leave behind: adjacent layers of the same material, and vanishingly thin “ghost” layers that contribute nothing. It merges the same-material neighbours into one layer, removes anything below your thickness threshold, and repeats until the design is stable (a removed middle layer can leave two same-material neighbours touching, which the next pass catches). You can then re-refine to settle the merit function after the structure has changed.

Locked layers are never merged or removed.

Settings

Minimum thickness (nm) — layers thinner than this are removed (typically 1–5 nm; raise it to your manufacturing minimum for a final pass).

Merge adjacent — combine neighbouring layers of the same material into a single layer.

Clean back — apply the same cleanup to the back-surface stack.

Re-optimize after — run a Refinement pass on the cleaned design to recover any merit lost to the structural change (on by default).

Refine iterations — how many refinement steps the post-clean pass runs (default 80).

How to read it

The operations preview lists exactly what will change before you commit — for example removing a thin layer or merging one layer into its neighbour — along with the merit function before and after. A separate thin layers panel shows which layers are currently below the threshold, as a diagnostic view. Apply performs the cleanup (and the optional refine) as a single undoable step.

A good habit is two-stage cleanup: a first pass at the synthesis floor to drop noise layers, then a second pass at your real manufacturing floor for the final design. Symmetric designs mirror the cleaned front onto the back automatically.

References

• H. A. Macleod, Thin-Film Optical Filters, 5th ed., §13.