chore: Remove deprecated complex fields nonlinearity

[caseyflex]

This old implementation has been deprecated since v2.8. It is time to remove support for it.

Some other changes:

• n0 (if specified) must be real

Greptile Overview

Updated On: 2025-10-29 19:37:06 UTC

Greptile Summary

This PR removes the deprecated use_complex_fields parameter from nonlinear models (TwoPhotonAbsorption and KerrNonlinearity), completing the transition to the real-field implementation introduced in Tidy3D v2.8. The changes simplify the codebase by:

• Changing beta and n2 fields from Complex to float types (real-valued only)
• Changing n0 from Optional[Complex] to Optional[float]
• Removing all complex-field validation logic and associated validators
• Removing the warning about using deprecated complex fields
• Updating all JSON schemas to reflect the new type constraints
• Removing tests for the deprecated functionality
• Adding a new _consistent_models validator to ensure n0 is consistent across models

The implementation is clean and thorough, with consistent updates across code, schemas, and tests. One minor issue was found: an error message is missing the actual value of n0 in the interpolation.

Confidence Score: 4/5

• This PR is safe to merge with minimal risk after addressing the error message formatting issue
• The PR cleanly removes deprecated functionality with thorough updates across all affected areas (code, schemas, tests). The implementation is straightforward and consistent. Score is 4 instead of 5 due to one syntax error in an error message and a minor style suggestion for the changelog.
• Pay attention to tidy3d/components/medium.py:640-642 for the error message formatting fix

Important Files Changed

File Analysis

Filename	Score	Overview
tidy3d/components/medium.py	4/5	Removed deprecated use_complex_fields field and associated validation logic from TwoPhotonAbsorption and KerrNonlinearity. Simplified type signatures to use only real numbers. Found one error message formatting issue.
tidy3d/components/simulation.py	5/5	Removed warning about deprecated use_complex_fields=True. Clean removal with no issues.
tests/test_components/test_medium.py	5/5	Removed tests for deprecated complex field functionality. Tests are properly cleaned up.
CHANGELOG.md	4/5	Added changelog entry for deprecated field removal. Entry could be improved with more specific details and proper categorization.
schemas/Simulation.json	5/5	Schema properly updated to remove use_complex_fields and change beta and n2 from complex to real number types.

Sequence Diagram

sequenceDiagram
    participant User
    participant TwoPhotonAbsorption
    participant KerrNonlinearity
    participant NonlinearSpec
    participant Medium
    participant Simulation

    Note over TwoPhotonAbsorption,KerrNonlinearity: Removed use_complex_fields field
    Note over TwoPhotonAbsorption: beta: Complex → float
    Note over KerrNonlinearity: n2: Complex → float
    Note over TwoPhotonAbsorption: n0: Optional[Complex] → Optional[float]
    Note over KerrNonlinearity: n0: Optional[Complex] → Optional[float]

    User->>TwoPhotonAbsorption: Create with beta (real only)
    TwoPhotonAbsorption->>TwoPhotonAbsorption: Remove _validate_beta_real
    TwoPhotonAbsorption->>TwoPhotonAbsorption: Simplify _validate_medium
    TwoPhotonAbsorption-->>User: Instance created

    User->>KerrNonlinearity: Create with n2 (real only)
    KerrNonlinearity->>KerrNonlinearity: Remove _validate_n2_real
    KerrNonlinearity->>KerrNonlinearity: Remove _validate_medium_freqs
    KerrNonlinearity-->>User: Instance created

    User->>NonlinearSpec: Create with models
    NonlinearSpec->>NonlinearSpec: Remove _consistent_old_complex_fields
    NonlinearSpec->>NonlinearSpec: Add _consistent_models (validates n0)
    NonlinearSpec-->>User: Spec created

    User->>Medium: Create with nonlinear_spec
    Medium->>NonlinearSpec: Validate models
    Medium-->>User: Medium created

    User->>Simulation: Create with nonlinear medium
    Simulation->>Simulation: Remove use_complex_fields warning
    Simulation-->>User: Simulation ready

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[greptile-apps]

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[caseyflex]

@greptile

[greptile-apps]

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[github-actions]

Diff Coverage

Diff: origin/develop...HEAD, staged and unstaged changes

• tidy3d/components/medium.py (94.7%): Missing lines 634

Summary

• Total: 19 lines
• Missing: 1 line
• Coverage: 94%

tidy3d/components/medium.py

Lines 630-638

  630     @pd.validator("models", always=True)
  631     def _consistent_models(cls, val):
  632         """Ensure that parameters shared between models are consistent."""
  633         if val is None:
! 634             return val
  635         n0 = None
  636         for model in val:
  637             if isinstance(model, (KerrNonlinearity, TwoPhotonAbsorption)):
  638                 if model.n0 is not None:

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[momchil-flex]

Nice cleanup. @yaugenst this is breaking compatibility of course but I suggested going through with it because we've had deprecation warnings for a while, and it's both not correct to use complex fields and making planned expansions harder.

[yaugenst-flex]

Thanks @caseyflex LGTM. Agree with @momchil-flex it's fine here especially since it has been deprecated for a while. My only minor nit is that it'd be better to be more specific about when something is going to be removed, but that's not for this PR to sort out 😬