| The terahertz (THz) radiation has been widely investigated during the past threedecades thanks to the development of ultrashort laser and terahertz time-domainspectroscopy (THz-TDS). Terahertz science and technology has become a significantresearch advance. Besides the terahertz sources and detectors, effective control of theterahertz propagation has attracted lots of interests. In recent years, different kinds ofterahertz devices have been explored. Photonic crystals (PCs), with periodicstructures and novel optical properties, can mold the flow of light. By designing thestructures of PCs in terahertz region, controlling terahertz radiation can be realizedas required.In this thesis, the terahertz PCs were designed and fabricated with paper, andthe transmission properties were characterized by THz-TDS. The main work in thisthesis is presented as follows:1. Four kinds of terahertz PCs were fabricated with paper layer by layer usingfemtosecond laser direct writing and then optimally assembled. They have differentlattice structures, which are one-dimensional (1D) stacks, two-dimensional (2D)square and triangular lattices as well as three-dimensional (3D) body-centered cubic(bcc) lattice.2. The terahertz transmission spectra of all PCs were measured using THz-TDS.The experimental results are compared with the numerical simulation and photonicband structures calculated with the plane wave expansion method. In1D PCs, thedefects and defect modes were investigated. In2D square lattice PC, thetransmission spectra of different polarizations were measured. In2D triangularlattice PC, the incident angle dependence of transmission spectrum and the linedefect were studied. In3D bcc PC, the slight asymmetry of lattice was observed inthe transmission spectra. All experimental results are reproduced by the numericalsimulation and explained by the photonic band structure well, indicating that the paper PCs can effectively control the propagation of terahertz wave as designed. |
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