Microstructural design for 2D photonic crystals with large polarization-independent band gaps

We propose a new approach to design photonic crystals (PhCs) with large complete photonic band gaps (CPBGs). By superposing two specific photonic structures with independent TE and TM band gaps, a heuristic design with CPBG is created. Then the CPBG is maximized using topology optimization method. This design method is verified for both square and hexagonal lattices, and several innovative structures with wide CPBGs are obtained. One of them presents the largest ever reported CPBG in 2D PhCs. The geometric characteristics of these innovative designs are discussed.