OptiClear: Differentiable Curvilinear Design Rule Legalization for Inverse-Designed Photonic Devices

2026-07-03

AI Summary

Photonic devices designed via inverse design often exhibit highly curved geometries that violate fabrication constraints, rendering them impractical for tape-out. To address this challenge, this work proposes OptiClear, the first framework enabling efficient and differentiable design-rule legalization tailored specifically for curved photonic structures. OptiClear integrates two complementary components: a rule-based morphological legalizer (OptiClear-R) and a differentiable legalizer (OptiClear-D). Leveraging custom GPU-accelerated differentiable morphological operators, morphology-guided mask processing, and constraint-aware optimization strategies, the framework reduces design rule violations from thousands to zero across multiple device types, while minimizing geometric distortion and preserving excellent optical performance.

Abstract

Photonic inverse design enables ultra-compact, high-performance devices with highly curvilinear and non-intuitive geometries, but the resulting layouts often violate fabrication design rules and hinder foundry manufacturing. Legalization methods designed for rectilinear Manhattan electrical layouts are not directly applicable to curvilinear inverse-designed photonic devices. Meanwhile, existing fabrication-aware inverse-design methods apply soft penalties on small features and sharp curvatures, but still cannot guarantee design-rule-compliant final layouts. In this work, we present OptiClear, a curvilinear design rule legalization framework for inverse-designed photonic devices. OptiClear provides two complementary legalization engines: OptiClear-R, a rule-based morphological legalizer that efficiently resolves violation regions through iterative morphology-guided mask processing, and OptiClear-D, a differentiable legalizer that formulates legalization as a minimum-distortion mask optimization problem under morphological stationary-point constraints, explicitly seeking a rule-compliant layout with minimal geometric deviation from the original design. We further develop customized differentiable morphological GPU operators that significantly improve the scalability of high-resolution mask legalization. Comprehensive evaluation across diverse inverse-designed photonic devices and a wide range of design-rule settings shows that OptiClear reduces design-rule violations from thousands to zero. The rule-based legalizer offers high runtime efficiency, while the differentiable legalizer more faithfully preserves the original optical functionality. This work establishes curvilinear design rule legalization as a practical post-design electronic-photonic design automation (EPDA) stage for translating high-performance inverse-designed photonic layouts into manufacturable tape-out-ready devices.

Problem

• inverse design
• photonic devices
• design rule compliance
• curvilinear geometry
• manufacturability

Innovation

• differentiable legalization
• curvilinear design rules
• inverse-designed photonics
• morphological optimization
• GPU-accelerated EPDA