Friday, October 20, 2017
Jessica L. Boland, A. Casadei, G. Tütüncouglu, F. Matteini , C. Davies, F. Gaveen, F. Amaduzzi, H.J. Joyce, L.M. Herz, A. Fontcuberta i Morral, Michael B. Johnston
Reliable doping in semiconductor nanowires is essential for the development of novel optoelectronic devices. Dopant incorporation within the nanowire can allow for optimisation of key optoelectronic properties, such as electron mobility and carrier lifetime. Thus, in-depth characterisation of doping mechanisms in semiconductor nanowires and their effect on the nanowire optoelectronics properties is crucial. However, extraction of the dopant concentration by conventional electrical methods remains difficult due to the associated challenges with fabricating lateral contacts onto the nanowire. In this work, we present a non-contact technique based on optical pump terahertz-probe spectroscopy for examining the extrinsic carrier concentration and optoelectronic properties of semiconductor nanowires. By extracting the temperature-dependent charge carrier dynamics, we show for the first time that the dopant activation energy and underlying scattering mechanisms affecting charge carrier mobility in these nanostructures can be determined via terahertz spectroscopy.
Shi Jia, Xianbin Yu, Hao Hu, Jinlong Yu, Toshio Morioka, Peter U. Jepsen, Leif K. Oxenløwe,
A photonic multi-channel terahertz (THz) wireless transmission system in the 350-475 GHz band is experimentally demonstrated. The employment of six THz carriers modulated with 10 Gbaud Nyquist quadrature phase-shift keying baseband signal per carrier results in an overall capacity of up to 120 Gb/s. The THz carriers with high-frequency stability and low phase noise are generated based on photonic photomixing of 25-GHz spaced six optical tones and a single optical local oscillator derived from a same optical frequency comb in an ultrabroadband uni-travelling carrier photodiode. The bit-error-rate performance below the hard decision forward error correction threshold of 3.8×10-3 for all the channels is successfully achieved after wireless delivery. Furthermore, we also investigate the influence of the harmonic spurs in a THz receiver on the performance of transmission system, and the experimental results suggest more than 30 dB spur suppression ratio in downconverted intermediate frequency signals for obtaining less than 1 dB interference.
Thursday, October 19, 2017
Brown University researchers have improved the resolution of terahertz emission spectroscopy — a technique used to study a wide variety of materials — by 1,000-fold, making the technique useful at the nanoscale.
Biao Wang, Dong Wu, Hai Zhu, Huibin Zhou, Jian Wei, Nan Lin Wang, Jiasen Niu, Ping Zheng, Yingxin Wang, Yingying Niu, Yu Quan Su, Ziran Zhao
Light probe from Uv to THz is critical in photoelectronics and has great applications ranging from imaging, communication to medicine. However, the room temperature ultrabroadband photodetection across visible down to far-infrared is still challenging. The challenging arises mainly from the lack of suitable photoactive materials. Because that conventional semiconductors, such as silicon, have their photosensitive properties cut off by the bandgap and are transparent to spectrum at long-wavelength infrared side. Comparatively, the dielectrics with very narrow band-gap but maintain the semiconductor-like electrical conduction would have priorities for ultrabroadband photodetection. Here we report on EuSbTe3 is highly sensitive from ultraviolet directly to terahertz (THz) at room temperature. High photoresponsivities 1 ~ 8 A W-1 reached in our prototype EuSbTe3 detectors with low noise equivalent power (NEP) recorded, for instances ~ 150 pW Hz-1/2 (at λ = 532 nm) and ~0.6 nW Hz-1/2 (at λ = 118.8 µm) respectively. Our results demonstrate a promising system with direct photosensitivity extending well into THz regime at room temperature, shed new light on exploring more sophisticated multi-band photoelectronics