Abstract-Two-colour THz quantum well photodetectors

 Haixia Wang,  Rong Zhang, Feng Wang, Zhejing Jiao, Dixiang Shao,   Zhanglong Fu, Tao Zhou,  Zhiyong Tan, Jungcheng Cao.

http://ieeexplore.ieee.org/document/8011679/

Two-colour terahertz (THz) quantum-well photodetectors are designed, fabricated, and characterised. To realise two-colour detection, a stacked structure is adopted by sequentially growing two one-colour detectors. It is found that the spectra of the stacked device are in accordance with those of the two individual detectors connected in series. The relatively broad spectral bandwidth may enable its use in a THz spectrometer

Abstract-A Terahertz Controlled-NOT Gate Based on Asymmetric Rotation of Polarization in Chiral Metamaterials

Wei-Zong Xu, Ya-Ting Shi, Jiandong Ye, Fang-Fang Ren, Ilya V. Shadrivov, Hai Lu, Lanju Liang, Xiaopeng Hu, Biaobing Jin, Rong Zhang, Youdou Zheng, Hark Hoe Tan, Chennupati Jagadish

http://onlinelibrary.wiley.com/doi/10.1002/adom.201700108/abstract

Logical operation based on polarization encoding of light is important for future data transmission and information processing. However, in the terahertz (THz) region, chiral materials with large optical activity are not available in nature, and the effective manipulation of polarization states remains challenging. Here, the authors demonstrate a double-layer bi-anisotropic metamaterial that consists of planar spiral and cut-wire layers separated by a polyimide film. Strong asymmetric polarization rotation of two orthogonal linear polarizations can be observed around 0.53 THz. By investigating the correlation between two linear polarization states before and after the spiral-wire metamaterial at this frequency, a controlled-NOT (CNOT) gate operating on two linear-polarization-based qubits is further exploited. The processing mechanism of the asymmetric rotation and CNOT gate is attributed to the scattering of dipole momentum based on classical multipole theory. This polarization processor's architecture is promising for robust and energy-efficient THz polarization control, and also provides an effective path for the development of future optical supercomputing technology.

Abstract-Temperature dependence of the point defect properties of GaN thin films studied by terahertz time-domain spectroscopy

• HeNan Fang, 
• Rong Zhang, 
• Bin Liu, 
• YeCao Li, 
• DeYi Fu, 
• Yi Li, 
• ZiLi Xie, 
• Zhe Zhuang, 
• YouDou Zheng,
• JingBo Wu, 
• BiaoBing Jin, 
• Jian Chen, 
• PeiHeng Wu, 

• http://link.springer.com/article/10.1007%2Fs11433-013-5202-6

The dielectric functions of GaN for the temperature and frequency ranges of 10–300 K and 0.3–1 THz are obtained using terahertz time-domain spectroscopy. It is found that there are oscillations of the dielectric functions at various temperatures. Physically, the oscillation behavior is attributed to the resonance states of the point defects in the material. Furthermore, the dielectric functions are well fitted by the combination of the simple Drude model together with the classical damped oscillator model. According to the values of the fitting parameters, the concentration and electron lifetime of the point defects for various temperatures are determined, and the temperature dependences of them are in accordance with the previously reported result. Therefore, terahertz time-domain spectroscopy can be considered as a promising technique for investigating the relevant characteristics of the point defects in semiconductor materials.