Research On Tunable Microstructure Functional Devices For Terahertz Wave

In recent years, as the breakthrough of terahertz (THz,1THz=1012Hz) generation and detection technology, the advantages of THz waves show the great application prospects. Meanwhile, THz functional devices are indispensable in the THz application systems in practice. The rise of artificial electromagnetic microstructure provides a new opportunity of the THz functional devices. The researches on THz microstructure functional devices have become one of the most important frontiers in the field of THz science and technology.In this dissertation, on the basis of the summary on the progress of THz microstructure functional devices both at home and abroad, a variety of THz tunable filters, modulators, isolators and sensors based on THz photonic crystals and plasmonics have been theoretically and experimentally investigated. A series of scientific and technical issues involving THz materials, the physical mechanisms of THz transmission and manipulation, device designing, simulation, fabrication and experimental test have been studied comprehensively. The main achievements in this dissertation are summarized as follows:1. THz phase transition photonic crystal was proposed and fabricated. Three different artificial electromagnetic mechanisms (i.e. dielectric photonic crystals, metallic photonic crystals and the plasmonic array) were obtained in single microstructure device on experiment, and their mutual transitions and THz wave modulation were realized by the different optical pumping approaches.2. A THz modulator based on double Schottky gate array plasmonic waveguide was designed and fabricated, and THz wave modulation was realized in this device by electric control. This device exhibits two different modulation behaviors of a discrete jump and a continuous shift of resonance digs when applying positive and negative bias, respectively. Furthermore, the simulations well explain the shifting and coupling behaviors of the double plasmonic band branches with the changes of the Schottky barriers in this device. 3. Based on the research of THz magneto optical response of the gyromagnetic and gyroelectric materials, the mechanisms of magnetic field manipulation and one-way transmission for THz waves in magneto-optical microstructure device were investigated. Magnetic photonic crystal was proposed to realize THz broadband tunable filter and polarization controller, and three THz nonreciprocal device were further investigated:a magneto-silicon photonic crystal microcavity circulator; a periodic plasmonic waveguide isolator; and a metal magneto-optical plasmonic lens with the functions of the isolation and enhancement. In theory, it has been cleared that both THz magneto-optical effect of materials and the asymmetry of system are two indispensable conditions to form THz one-way transmission, and magneto-optic splitting effect caused by THz magnetoplasmons plays a key role in one-way transmission and enhancement in the magneto-optical microstructure.4. The guided resonance effect in photonic crystal column array was theoretically and experimentally demonstrated in the THz regime, the corresponding relationship between photonic band gap and guided resonance was found, and the effective medium theory and Fano resonance model were established for this resonance effect. Based on this effect, the qualitative analysis and real-time quantitative sensing for microfluidics were realized by THz time domain spectroscopy system.5. The THz dielectric property and magneto-optical effects of ferrofluids were experimentally investigated, discovering the relation between the refractive index and the concentration of magnetic nanoparticles in the ferrofluid and its magnetically induced birefringence. Furthermore, for a ferrofluid-filled photonic crystal, the magnetoplasmon resonance splitting and the magnetically induced transparency were demonstrated, which realized magnetically manipulating THz waves and the magnetic field sensing by THz technology.