| Recently, as terahertz technology keeps evolving at a galloping rate, more and more promising and valuable applications have been proposed and realized to utilize the specific characteristics of the terahertz band, such as terahertz communication, medical imaging, plasma diagnostics and something else. All of these potential applications need good multi-wavelength effect to increase the qualities of signals and limit the levels of noises as low as possible. But the existing ways such as metamaterial, quantum wells and photonic crystals have many disadvantages like high cost, sophisticated structure and difficulty to install or adjust. Thus, it is very necessary and meaningful to find a terahertz multi-wavelength device with high quality but low cost and mass production.In this work, several potential devices are propose to approach this aim and discussed in separate chapters.Firstly, the periodical hole array structures fabricated on an aluminum slab are experimentally investigated due to their extraordinary optical transmission. The terahertz time domain spectroscopy system is used to perform the transmission properties of two samples of same geometric dimension but different scale. Then the simulations based on the finite difference time domain method are applied to analysis the reasons which cause the extraordinary optical transmission. The analysis shows the extraordinary optical transmission is related to the resonance of surface plasmon polariton and the differences between big and small samples can attribute to the degrees of periodical extension and boundary conditions.Then, a photonic-crystal-like multi-cavity resonant system which is fabricated by silicon wafers and air spaces is introduced because of its great characteristic and low cost. We use three methods: backward wave oscillator system, transmission matrix method and Comsol software to obtain its transmission curves and transmission properties and their results agree with each other. All results imply this device is a high-quality triple-channel terahertz filter. The theories of modes splitting and modes hybrid are applied successful to explain the formation process. In addition, the blue shift of filter frequencies indicate this device has ability to tune in limited range.Besides, the parallel plate waveguides with cavities are studied for the phenomena of electromagnetically induced transparency. We use three methods: terahertz time domain spectroscopy system, scatting matrix method and Comsol software to get their transmission curves and transmission properties. By combining the experimental, theoretical and simulated results, we obtain the transmission characteristics of two dimensions. The results show that the devices can be used as high quality double-channel terahertz filter like channel switches. The theories of waveguide can well explain the emerging and disappearing of the transmission dips.Finally, an uncompleted work is exhibited in the last chapter to introduce the unique characteristics of a metal transmission line of compound-period. The simulated results obtained by using CST show this device can be used as double-channel terahertz filter which can also guide the electromagnetic wave in definite direction. What’s more, the samples and the experiment plans are made for the further measurement.To conclude, three verified and one promising approaches are proposed to meet the demands of high-quality but low-cost and mass-production terahertz filter and all of them have great applications values. Various methods are utilized to explain the mechanisms of their high qualities, hence this work has great reference price to design the similar devices. |
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