Abstract-Analytical model of terahertz metasurface for enhanced amplitude modulation

Jiawei Cong,Gaige Zheng, Zhiqiang Zhou,  Min Liu,   Mingyang Chen,  Hongbing Yao, Pengyu Wei,  Naifei Ren

http://iopscience.iop.org/article/10.1088/1361-6463/aad34d

Optically-driven terahertz (THz) modulation generally requires excitation of excessively large photoconductivity of active components, which poses huge challenges for realization and practical applications. With aid of an analytical circuit model, we demonstrate an approach to alleviate the trade-off between large amplitude modulation and use of low photoconductivity in complementary split-ring resonator modulators. As revealed by analytical results and verified by full-wave simulation, the maximum modulation depth and needed photoconductivity are determined by the inductance and gap resistance of the structure, respectively. Therefore, by tailoring its inductance and resistance via geometry adjustment, both improvement of modulation efficiency and reduction of photoconductivity are simultaneously realized. A large amplitude modulation ~0.5 is achieved with ultralow conductivity of 2000S/m. The proposed approach might offer a guideline for structure design of THz devices with various active components.

Abstract-Ultrastrong Terahertz Emission from InN Nanopyramids on Single Crystal ZnO Substrates

Huiqiang Liu, Zuxin Chen, Sheng Chu,Xuechen Chen, Min Liu, Nan Peng, Guang Chu, Feng Huang, Rufang Peng

http://onlinelibrary.wiley.com/doi/10.1002/adom.201700178/full

The creation of high efficiency and room temperature terahertz (THz) emitters has long been expected in both scientific and industrial communities. Despite the recent progress in THz source such as quantum cascade lasers, high efficiency THz emitters capable of operating at room temperature are still elusive. Indium nitride (InN), a narrow bandgap semiconductor, has emerged as a promising THz emitter due to its unique electronic properties. However, the efficiency of InN THz emitters reported up to now is still far from theoretically predicted because of inadequately engineered electrical conduction and radiative coupling. In this study, the authors report a novel, high performance THz emitting structure consisting of nanoengineered InN micro/nanopyramid arrays on a single crystal zinc oxide (ZnO) substrate. With improved electronic conduction from Zn diffusion induced doping and enhanced radiation coupling benefiting from uniquely structured geometry, the InN nanopyramids yielded THz emission intensity is close to an order of magnitude stronger than that of p-type indium arsenide (InAs). These findings prove that InN is a promising THz material and of wide importance in material science, optical engineering sectors, etc.