A Modularized and Switchable Component for Flexible Passive Device: Terahertz Photonic Crystals with Fine‐Tuning

Abstract In this work, tunable terahertz photonic crystals (PCs) used as modularized and switchable components in flexible passive device are designed and prepared. Flexible woodpile structures created by the direct‐writing technology with a composite ink system composed of barium strontium titanate nanoparticles and polydimethylsiloxane are immersed in 5CB liquid crystals (LCs), where the orientation of LC molecule is modulated by the external magnetic field. Each of these can work in terahertz wavelength with specific position and depth of the dips in the transmittance spectra due to different geometries as well as having the ability of fine‐tuning. Experiments show that the photonic gaps of these PCs can cover from 0.2 to 0.3 THz, as well as about 7.5% fine tunability of photonic gap appearing with the orientation change of the magnetic field. More interestingly, the dips of photonic gaps keep the same position but become deeper with the increase of layer, an ability to realize another dimensional switchover. This work demonstrates that efficient terahertz PCs with different geometry parameters could be dynamically tuned by the orientation of magnetic field and it can open a universal approach to shrinking the size of device and rapid manufacturing in a large throughput.