The Structural Optimizer searches over the structure of a design rather than just its thicknesses. Each step it randomly mutates the layer stack — by adding, removing, splitting, merging, or perturbing a layer — re-refines the result, and decides whether to keep it using a simulated-annealing rule. Because it can change the number and arrangement of layers, it reaches designs that fixed-structure Refinement and even the insertion-based Needle and Gradual Evolution tools cannot.
Each generation it proposes several mutations of the current design, refines each one, and takes the best of the batch. A worse design may still be accepted with a probability set by a temperature that cools as the run progresses — this is what lets the search climb out of a local minimum. The live design always tracks the best result found, so stopping, resetting, or switching tabs always leaves you on the best design.
| Mutation | Effect |
|---|---|
| Add | Insert a new layer (material from the pool) at a random position. |
| Remove | Delete a layer. |
| Split | Cut one layer into two. |
| Merge | Combine adjacent layers. |
| Perturb | Jitter a layer’s thickness. |
Locked layers are never touched, and thickness bounds are always respected.
Settings
Section titled “Settings”Candidate pool — the materials the add and split operators may use (All / Clear).
Mutation kinds — toggles for which operators the search is allowed to use.
Max iter — the most generations to run.
Target MF — stop once the merit function reaches this value.
T₀ (temperature) — the starting annealing temperature. Higher values accept more uphill moves early on, which widens the search.
Jitter — the thickness perturbation scale for the perturb operator.
Refine iterations — how many refinement steps are applied to each proposed design.
dMin — the minimum thickness for layers that are added or split.
Max add / Max layers — caps on how far the design may grow.
Parallel K — how many proposals are refined together each generation.
Inner refiner — which method refines each proposal. See Optimization Methods for the choices.
Minimum and maximum thickness limits are relaxed during the search; re-enable them with a Refinement and Design Cleaner pass afterwards.
How to read it
Section titled “How to read it”The MF trend chart plots both the best and the current merit against generation, and an accepted-improvements history lists each new best alongside the mutation that produced it. A Pareto / Top-Designs panel lets you compare the best designs found. Best restores the global best at any time.
The tool shines on designs with room to restructure (for example a multi-layer anti-reflection coating); on a single-layer design there is nothing structural to do, so use Refinement instead. A good pattern is to run it to discover a better topology, then finish with Refinement at your manufacturing floor.
References
Section titled “References”- S. Kirkpatrick, C. D. Gelatt, M. P. Vecchi, Science 220, 671 (1983).
- A. V. Tikhonravov & M. K. Trubetskov, Appl. Opt. 51, 7319 (2012).
- H. A. Macleod, Thin-Film Optical Filters, 5th ed., Ch. 9.