Topology Optimization Enabled High Performance and Easy-to-Fabricate Hybrid Photonic Crystals

Photonic crystals (PtCs) can confine and guide electromagnetic waves within specific frequency ranges, forming the foundation for promising optical applications. To numerically design PtCs with broad bandgaps, materials with high dielectric constants are favored. However, fabricating these high dielectric constant materials into microstructures is extremely challenging and it suffers from limitation of low fabricating resolution. To address this problem, this paper proposes hybrid microstructures composed of an easy-to-fabricate core and a high dielectric constant coating layer, which leverages the strength of both materials. This paper establishes a topology optimization algorithm to generate these PtCs with maximized bandgaps. Numerical examples demonstrate the effectiveness of the proposed method in generating optimized unit cells for both transverse magnetic (TM) and transverse electric (TE) modes. The hybrid PtCs offer unprecedented opportunities for the fabrication of optical devices, encouraging further research on multimaterial optical systems and advanced optimization methods to explore photonic bandgap materials beyond those offered by the current photonic technology.