Study Of Terahertz Filter Devices Based On Metal Microstructure

With the rapid development and wide application of terahertz technology, the investigation of the terahertz modulation device becomes an important subject. The extraordinary transmission effect shown by the metal surface sub-wavelength periodic array structure exceeded the limits of the classical aperture diffraction theory, which has a great value in the field of photonics, optoelectronics and functional materials.Metal microstructures based on the above theory have a excellent adjustability for the optical transmission.Accordingly, the metal microstructures can be used in the terahertz filter.The existing experience of the data modeling and experimental measurements provide some methods and ideas for the design of metal microstructure.In this paper,from two aspects oft he numerical simulations and experimental measurements,the terahertz transmission characteristics of the metal aperture, cross hole, rectangular hole and double H series structure are studied.The result gives a reference and basis for the development of terahertz filters. The main work in this thesis includes the following points:1.The periodic metalaperturesare simulated numerically and measuredexperimentally.The results show that this kind of structure has a transmission peak of in the terahertz band.With the increasing of the radius of aperture, the transmission peak’s position shift toward the low frequency, while the full width at half maximum(FWHM) of spectrum increases. With increasing of the period of structures, the transmission peak’s position shift toward the high frequencies, while their FWHM increases.2. We numerically simulated and experimentally measured THztransmission of periodic metal cross holes array. The results show that this kind of structures also has a transmission peak in the terahertz band.With the increasing of cross side-length, the transmission peak’s position shift toward the lower frequency, the FWHM of spectrumincreases. Underthe structure size of T=90μm, w=10μm, and I=80μm of the metal cross hole,this kind of metallic cross hole array can be used as a typical terahertz band pass filter. 3. We numerically simulated and experimentally measured the periodic metalrectangular holesarray structure in the different incident modes of THz radiation.When the direction of incident electric field parallel to the long side of rectangular hole, and the other size parameters of rectangle hole keep as a constant, THz transmission peak’s position shift toward the lower frequency with increasing of the size of short edge. It is worth to note that, when the ratio of short side with the long side is extremely small, THz transmission of this structure is almost zero. When the incident electric field is perpendicular to the direction of long side of rectangular holes, a transmission peak occurs for a same length-short-ratio of structure.When the direction of the incident electric field parallel to the long sides of rectangular holes, and two sides size of structure unchanged, the THz transmission peak’s position shift toward the lower frequency and the FWHM of transmission spectrum increases with increasing of the period of array. When the incident electric field is perpendicular to the longitudinal direction, the transmission peak’s position is unchanged and the FWHM decreases.4.For the dual H-series metal structure, the THz transmission of H-l type array shows a single-wide band,while the H-Ⅱ type shows a dual-band structure, where the first pass band is narrower.So the lower resolution of our experimental system is not enough to measure this pass band. At the same time, the H-Ⅲ type of array shows a tri-band structure in the terahertz band.In summary, the terahertz transmission characteristics of the metalarray structures of aperture, cross hole, rectangular hole and dual H series are studied by the theoretical modeling and experimental measurements inthis paper. The results provide a theoretical basis and numerical reference for the fabrication of terahertz filter.