Tunable Ultra-narrow Bandwidth Terahertz Filters

With the rapid development of terahertz(THz) technology, it has attracted great attention of researchers over the last decade. It was named "technology to change the future of the world’s top ten" by the US government in 2014. In general,THz technology includes THz communication technology, THz radar and THz imaging technology etc. THz filter was widely used in many application systems of THZ,where filtering specified frequencies band of the system(such as a terahertz band-stop filter) or to obtain a specific frequency band(such as a band-pass filter). This paper reviews the development of THZ filters in recent years,the simulation method of scattering,transmission and reflection of THZ system computed by using the Frequency Domain Finite Integration, we proposed two kinds of terahertz filters based on the periodic subwavelength metal structure,we used numerical simulations to investigate the performance of the devices. Our main work and innovations are as follows:First, we proposed a terahertz band-stop filter based a periodic metal micro structure, By numerical simulation,the minimum transmission factor of the band-stop filter at the resonant frequency is 0.5%, and the stop band width is 9GHz, and the resonant frequency is 4.17 THZ.We could manipulate the filter frequency of the band-stop filter by adjusting the period of the periodic structure and the incidence angle of the terahertz wave demonstrating the tunable stop band of the terahertz band-stop filter.Second, we proposed a terahertz band-pass filter based a periodic metal micro structure. By numerical simulation,the maximum transmission factor of the band-pass filter at the resonant frequency is 99%, and the pass band width is 0.125 THZ, and the resonant frequency is3.646 THZ.We could manipulate the filter frequency of the band-pass filter by changing the structure size of the metal micro structure or by adjusting the incidence angle of the terahertz waves demonstrating the tunable pass band of the terahertz band-pass filter.The main work of this paper was to study characteristics of the above two kinds of terahertz filter, The paper has two finding: 1,The proposed terahertz filter has many features such as simple structure,narrow bandwith and good filter performance. 2, We could tune the bandwidth of the filter by adjusting the period of THZ filters.