Abstract- Optically tuneable broadband terahertz metamaterials using photosensitive semiconductor material

Qinglong Meng, Yan Zhang, Zheqiang Zhong, Bin Zhang

https://www.tandfonline.com/doi/abs/10.1080/09500340.2018.1496288?journalCode=tmop20

We present optically tuneable broadband terahertz metamaterials consisting of photosensitive semiconductor material. The characteristics of semiconductor materials are very important for terahertz functional devices, which is strongly dependent on the photoexcited carriers in semiconductor materials. Based on the model of the generation of the carriers in semiconductor materials, the tuneability of the resonance frequency and resonance strength in terahertz metamaterials under the femtosecond laser pulse has been analysed. The experimental results of the transmissivities of several bare semiconductor materials show that GaAs semiconductor could be a potential candidate for broadband terahertz functional devices design. Moreover, the simulation results of the resonance frequency increase with the increase of the laser fluence, whereas the resonance strength near the resonance frequency is significantly weakened with the increase of the laser fluence. Meanwhile, the modulation depth can be reached approximately 90% at 1.24 THz. Our proposed broadband tuneable terahertz metamaterials have numerous potential applications, including terahertz modulator, absorber and switches.

Abstract-A broadband tunable terahertz negative refractive index metamaterial

Fang Ling, Zheqiang Zhong, Renshuai Huang,  Bin Zhang

https://www.nature.com/articles/s41598-018-28221-3

A strategy to greatly broaden negative refractive index (NRI) band, reduce loss and ease bi-anisotropy of NRI metamaterials (MMs) has been proposed at terahertz frequencies. Due to the symmetric structure of the MM, the transmission and refractive index are independent to polarizations of incident radiations, and a broadband NRI is obtainable for the range of the incident angle from 0° to 26°. In addition, THz MMs’ properties such as transmission, phase and negative refraction exhibit a real-time response by controlling the temperature. The results indicate that the maximum bands of the negative and double-negative refraction are 1.66 THz and 1.37 THz for the temperature of 40 °C and 63 °C, respectively. The figure of merit of the MMs exceeds 10 (that is, low loss) as the frequency increases from 2.44 THz to 2.56 THz in the working temperature range, and the maximum figure of merit is 83.77 at 2.01 THz where the refractive index is −2.81 for a given temperature of 40 °C. Furthermore, the negative refraction of the MMs at the low loss band is verified by the classical method of the wedge, and the symmetric slab waveguide based on the proposed MM has many unique properties.

Abstract-Thermally tunable broadband terahertz metamaterials with negative refractive index

Weili Li, Qinglong Meng, Renshuai Huang, Zheqiang Zhong, Bin Zhang

https://www.sciencedirect.com/science/article/pii/S0030401817310945

A thermally tunable broadband metamaterials with negative refractive index (NRI) is investigated in terahertz (THz) region theoretically. The metamaterials is designed by fabricating two stand-up opposite L shape metallic structures on fused quartz substrate, and the indium antimonide (InSb) is filled in the bottom gap of the two L shape structures. The tunability is attributed to the InSb because the InSb can changes the capacitance of the gap area by adjusting the temperature. The transmission characteristics and the retrieved electromagnetic parameters of the metamaterials are analyzed. Results indicate that the resonant frequency and amplitude modulation of the metamaterials can be tuned continuously in broadband range (about 0.62 THz), and the phase modulation from −2$\mathrm{}$ to 3 rad is also achieved within broadband range (about 0.8 THz). In addition, the metamaterials shows dual-band NRI behaviors at 0.4$\mathrm{}\mathrm{}$–0.9$\mathrm{}\mathrm{}$ THz and 1.06$\mathrm{}\mathrm{}$–1.15$\mathrm{}\mathrm{}$THz when the temperature increases to 400 K. The wedge-shaped prism simulations are implemented to verify the NRI characteristics and indicate that the NRI of the metamaterials can be achieved.