Optimizer

Optimizer is used to search automatically for a better parameter set. On this page, define optimization objectives, search variables, an optional grid pre-search (Grid Parameters), and local solver configuration (Algorithm Parameters), then execute Run Optimizer from the top toolbar.

This page defines the optimization task. It does not interpret the final outcome. After the run finishes, go to Optimization Report in the results area to inspect the best solution, evaluation history, and objective breakdown.

Prerequisites

• Structure passes validation.
• Optics passes validation.
• The optimization goal and desired direction are clear (anti-reflection, transmission enhancement, spectrum matching, etc.).

Recommended Configuration Order

1. Define Objectives first (target quantity, incident light, scoring method).
2. Define Variables (searchable parameters and bounds).
3. Tune Grid Parameters (optional grid pre-search).
4. Tune Algorithm Parameters (solver and convergence settings).
5. Use a small-budget first run, then increase budget only after the direction is validated.

Page Structure

The Optimizer page is divided into four vertical sections:

The upper half contains the objectives and variables sections (empty-state example):

The lower half contains the grid parameters and algorithm parameters sections:

Global Toolbar

• Run Optimizer is available only when the entire model is valid.
• Once the run starts, all input controls on this page are locked.
• If this page contains errors, the footer groups them under Optimizer and keeps the run entry disabled.

Optimization Objectives

The objectives section defines what "better" means. All enabled objectives are combined into one weighted fitness score.

Toolbar

Objective List Table

The list table shows a summary for each objective. Double-click a row or click the Edit button to open the editor dialog.

Below is a complete example with 3 objectives (mixed Point and Band modes) and the Wavelength Coverage Preview:

Mode Derivation Logic

The Mode badge in the objective list is derived automatically from the current configuration; no manual selection is needed:

Target Color Coding

The objective list table and Wavelength Coverage Preview use a unified color scheme:

Wavelength Coverage Preview

Below the objective list is a collapsible Wavelength Coverage Preview panel that visualizes each objective's wavelength range as horizontal bars.

Below is the Wavelength Coverage Preview with a single objective (displayed as a dot marker):

With multiple objectives, the preview panel shows multiple bars with overlap annotations in summary text:

Multi-Objective Best Practices

Core strategies for multi-objective optimization:

• Point + Band combination: Use a Point objective to lock the extremum at the design wavelength, and a Band objective to ensure broadband performance.
• Weight allocation: Higher Weight directs the solver to invest more optimization effort on that objective.
• Independent incident light: Each objective's incident light conditions are configured independently, allowing different angles and polarization states within the same optimization run.

Example for broadband anti-reflection coating design:

This configuration sets reflectance minimization at the design wavelength as the highest priority (weight 2), broadband average reflectance minimization as the secondary objective (weight 1), and transmittance maximization (weight 0.5) as a supplementary direction.

For curve fitting scenarios, add one objective in Curve Fit mode with a target spectral shape, and another using Scalar Goal to enforce a floor value (for example, Stay in Range mode to ensure reflectance does not exceed a threshold).

Objective Editor Dialog

Click the Edit button or double-click an objective row to open the editor dialog. The dialog has three sections: Target, Incident Light, and Optimization Goal.

Target Section

Select the physical quantity to optimize:

When Layer Absorption is selected, a secondary selector appears for choosing the target layer or layer group.

When Reflection Color or Transmission Color is selected, the system automatically switches to Sweep mode, enables incident spectrum, enables color calculation, and locks the Goal to Color Match.

Incident Light Section

Each objective has independent incident light conditions, separate from the global Optics page.

Wavelength Sampling

Color targets are forced to use Sweep mode.

Incident Angle

Range: 0 deg to 89.9 deg. Slider and numeric input are linked.

Polarization Ratio

Range: 0 to 1. 0 = pure s-polarization, 1 = pure p-polarization, 0.5 = unpolarized.

Cone Angle (Optional Module)

Models finite numerical aperture or divergent beams. When enabled:

Incident Spectrum (Optional Module)

Available only in Sweep mode. When enabled, the incident spectrum acts as wavelength weights for weighted averaging or weighted curve fitting.

For color targets, the incident spectrum is automatically enabled and requires configuring source and observer angle (2 deg / 10 deg).

Optimization Goal Section

The available goal type depends on the combination of Target and wavelength mode.

Scalar Goal

Available for all non-color targets.

In Single wavelength mode, no Aggregator is needed; the score is evaluated directly at that wavelength.

Curve Fit

Available only in Sweep mode. The goal is to match the optimized spectrum to a given target curve.

After the Apply operation, a status tag indicates the current data state:

Color Match

Automatically activated when Reflection Color or Transmission Color is selected.

Weight

Each objective has a Weight field (default 1, minimum 0.000001). When multiple objectives are used, weights determine each objective's share in the total fitness. Higher weight values direct the solver to invest more optimization effort on that objective.

Optimization Variables

The variable table defines which input parameters the solver is allowed to modify.

Toolbar

Variable Table Fields

Path Selection (CascadeSelect)

The CascadeSelect path picker shows two top-level categories: Structure (layers and layer groups) and Surroundings (incidence and transmission media). Expand each category to drill down to specific parameters.

The path picker uses a cascading menu that only shows currently enabled elements in the structure:

indexType and Optimizable Properties

The refractive index mode determines which properties can be used as optimization variables:

Initial Value and Grid Interaction

• When grid search is off: Initial Value serves as the starting point for the local solver and must be within the [Minimum, Maximum] range.
• When grid search is on: The Initial Value column is disabled; starting points are replaced by grid seeds.

Validation Rules

When Paths Become Invalid

Multi-Variable Configuration Example

When using grid search with 2 variables and 5 samples per variable, this produces 5^2 = 25 grid points. Each grid seed then gets refined by the local solver.

Grid Parameters

Grid search is an optional pre-search stage. When enabled, the optimizer first performs a coarse grid scan across the entire variable space, selects the top seeds, and then runs local optimization from each seed independently.

Behavioral Changes When Grid Is Enabled

Algorithm Parameters

Algorithm Selection

Common Parameters

TRF Parameters

L-BFGS-B Parameters

Nelder-Mead Parameters

Practical Tuning Guidance

Pre-Run Validation and Common Errors

Checklist before executing Run Optimizer:

1. At least one enabled and valid objective exists.
2. At least one enabled and valid variable exists.
3. No duplicate paths among enabled variables.
4. Structure and Optics pass validation.
5. Variable ranges are physically reasonable.
6. Algorithm parameters are within the allowed ranges.

After this page is configured, continue with the next chapter: Basic Optical Results. Read ordinary result interpretation first, then return later to Optimization Report for best-solution analysis.