Direct ink writing of three-dimensional Al2O3/polydimethylsiloxane photonic crystal heterostructures for terahertz frequencies

The photonic crystal heterostructures with multi-bandgap could manipulate multiple optical signals simultaneously, and have important applications in various multi-channel optical or optoelectronic devices. However, due to the limitations of materials and structure complexity, photonic crystal heterostructures for terahertz frequencies are rarely reported. Here, we report a facile and efficient approach to fabricate terahertz photonic crystal heterostructures (TPCHs) via direct ink writing (DIW) 3D printing technology. Al2O3/polydimethylsiloxane (PDMS) composite ink suitable for DIW has been developed. Al2O3/PDMS TPCHs with different structural parameters have been fabricated by DIW 3D printing. The results of simulation and experiments demonstrate that these TPCHs exhibit some special optical properties, such as bandgap deepening and dual-bandgap, compared with the conventional three-dimensional terahertz photonic crystals (3D-TPCs). The optical properties of TPCHs could be accurately regulated by varying the lattice constant of their compositional 3D-TPCs. The DIW 3D printing technology offers a new opportunity to create TPCHs with tailored photonic behavior for novel terahertz functional devices.