Angle tunable terahertz band notch filter with single-band and dual-band switching characteristics based on metallic strip structures

Terahertz (THz) science and technology has broad application prospects in the next generation wireless communication systems [1], imaging [2], bio-detection [3] and other fields. To satisfy the needs of applications in these fields, high-performance terahertz absorbers, highly sensitive terahertz detectors and multifunctional terahertz filters have attracted extensive research. In particular, the emergence of metamaterials have enriched the related THz devices. As a kind of artificial materials made up of an arrangement of sub-wavelength periodic cells, metamaterials shows a desired electromagnetic field response that is determined by the structure and spatial arrangement of the well-designed periodic cells [4], [5], [6], [7], [8], [9], [10], [11], [12]. Additionally, strong local resonances can be excited by the specific structures that provides a strategy for the manipulation of THz wave.

Since J. B. Pendry demonstrated the negative dielectric constants and permittivity respectively in 1990s [13], [14], metamaterials have led to the development of THz functional devices such as superlenses [15], perfect absorbers [16], [17], planar filters [18], [19], [20], and polarizers [21], [22], [23], [24], [25]. In particular, THz filters are a key component of terahertz high-speed wireless communication systems and terahertz imaging systems due to the capability of filtering out the undesired frequencies. Tunable property is one of the most important features that can actively control the resonant frequency or intensity of THz functional devices. According to the applied physical fields, tunable schemes based on optical [26], thermal [27], electrical [28], [29], and mechanical [30] manners are developed. In this regard, Huang et al. proposed a terahertz metamaterial bandpass filter based on vanadium dioxide to actively control the bandwidth, which realizes the bandwidth adjustment function by applying different bias voltages to induce the phase transition of different VO2 patterns [31]. Lan et al. fabricated metamaterial subsurfaces using composites composed of micro ceramic spheres, ferroelectric materials and polydimethylsiloxane, which allows thermally reversible tuning of this metamaterial due to the temperature dependent variation of the dielectric constant of the ferroelectric composition [32]. Ling et al. used aluminum rings and photosensitive ring-shaped silicon apertures to form a tunable terahertz negative refractive index metamaterial, and the transmission characteristics of the metamaterial were tuned from low-pass to high-pass with increasing silicon conductivity, and continuous tuning was achieved for the corresponding phase in the low frequency band [33]. In these demonstrations, additional equipment is required to support the external physical conditions, leading to a complicated experimental setup. Liu et al. proposed an angle tunable THz filter based on multiplexed metallic bar resonators [34], which provides a simple and feasible method for THz filtering. In addition, the multi-resonance property of THz filters is another key factor in communication systems. A common strategy for increasing the resonant point is to incorporate multiple resonant structures into the metamaterial unit cells. This increases the complexity of design and fabrication, meanwhile makes it difficult to tune the individual resonant dips.

In this work, we propose and experimentally demonstrate an angle tunable terahertz band notch filter based on bimetallic band metamaterial structure. The proposed device consists of two metal rods and a glass substrate. We studied the resonance characteristics of metal rods with different lengths and the performance of their combination. The dual frequency THz filtering function is realized by multiplexing the metal rod structure, and the resonance depth can be individually tuned by rotating the metal rod structure. At the same time, we study the influence of the angle between the metal rods and terahertz polarization on the tunable transmission characteristics. In particular, the device shows a unique function of switching between single band and dual band resonance.

留言 (0)

沒有登入
gif