Qi-Ye Wen

Guest Editorial TTA Special Section on Terahertz Materials and Devices

Qi-Ye Wen

Lying between radio frequency and infrared radiation, terahertz (THz) wave encounters lots of difficulties to produce, detect, transmit, and modulate. Great efforts have been made to construct THz devices, including sources, detectors, switches, modulators, lenses, and filters. However, only moderate progresses have been made in THz generation and detection. Furthermore, the devices and techniques to control and manipulate THz waves are still in its infancy. Therefore, it is still a challenge to date to develop sophisticated THz application systems such as communication, sensing, safety inspection, imaging and medical diagnose systems. This difficult position of THz wave is essential due to the deficiency of THz materials having a suitable THz electromagnetic response, as compared to its neighboring microwave and infrared regime. Practicable material will largely push the THz technology to real-world applications. The GaAs/AlxGa1-xAs material system, for example, is the heart of THz quantum cascade lasers. High quality NbN films, again, set the basis of THz hot electron bolometer.1

In this special section, we show how materials are fabricated and designed for THz devices. These devices include a THz emitter based on nitrogen-doped n-type 6H-SiC, and a THz switch fabricated with high-speed phase-transition material.

In the first paper, a powerful THz emitter that operated above room temperature in pulsed mode was developed from nitrogen doped n-type 6H-SiC. J. Kolodzey, a professor from University of Delaware, fabricated this THz emitter by predominantly doping n-type 6H-SiC wafer with high density Nitrogen donors. Due to the radiative bound exaction transitions associated with the nitrogen donor impurities, the THz output power and operating temperature were significantly improved as compared to previous reported dopant based emitters. The devices emit THz pulse at temperatures up to 333 K, which is the highest emission temperature reported for any dopant based terahertz emitter of which we are aware.

In the second paper, devices and techniques to control and manipulate THz waves were demonstrated with an interesting electron material: vanadium dioxide (VO2). VO2exhibits a reversible first-order phase transition from an insulating state to a metallic state under proper external stimulation. The ultrafast nature of the phase transition along with huge changes in the electrical/dielectric properties creates several possibilities for THz modulation devices such as modulators and switches. With VO2films, an ultrafast optical switching to THz transmission was realized with a switching ratio over 80% during a wide frequency range from 0.3 THz to 2.5 THz.

As the guest editor of this issue, I would like to express my sincere thanks to the authors for their contributions to this special section. I also appreciate the assistance of the editorial staffs for their great efforts on making this special section to be pressed in time.

Qi-Ye Wen,Guest EditorUniversity of Electronic Science and Technology of China

Chengdu, China

Qi-Ye Wenreceived his B.S. degree from Wuhan University of Technology, Wuhan in 1998, the M.S. degree from Guangxi University, Nanning in 2001, and the Ph.D. degree from University of Electronic Science and Technology of China (UESTC), Chengdu in 2005. He is now a professor with the School of Microelectronic and Solid-state Electronics, UESTC. He has published more than 100 journal papers with an H-index of 16. One of his papers on THz absorber was selected as the ESI High Cited Paper. His research interests include electronic materials and devices for THz wave manipulation, and THz communication and imaging. He was the recipient of Sichuan Outstanding Younger Research Foundation from Sichuan Province, and the New Century Excellent Talents Program Award from the Ministry of Education of China.

Digital Object Identifier: 10.3969/j.issn.1674-862X.2014.03.001