Abstract-Coherent detection for continuous terahertz wave

Hui Yuan, Tielin Lu, Jingshui Zhang, Yuejin Zhao

Beijing Institute of Technology (China)

Liangliang Zhang, Ji Zhao

Capital Normal Univ. (China)

Proc. SPIE 9585, Terahertz Emitters, Receivers, and Applications VI, 95850O (August 31, 2015); doi:10.1117/12.2187465

http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2434792

In this paper we demonstrated a coherent raster-scan imaging system that can acquire phase information based on continuous terahertz imaging. It mixes the terahertz with a Fs-laser by a electro-optic crystal of ZnTe to make a hybrid modulation on the crystal to achieve continuous terahertz detection. In this way, it can not only propagate for a long distance but also achieve phase detection for continuous terahertz imaging. The surface images of objects that are under test can be obtained by the Backward-Wave Oscillator, which the output power is 10mW at 205.994GHz. With the repetition frequency of 80MHz, the output power of the MaiTai is 1.65W and 100fs pulse light at 800nm. The images can achieve diffraction-limited resolution approximately. And the simulated results show that the system can obtain phase imaging of test objects based on continuous terahertz source. The way to get the phase of the signal has significant meaning for coherent detection of continuous terahertz source.
 © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Abstract-Terahertz-to-infrared emission through laser excitation of surface plasmons in metal films with porous nanostructures

Liangliang Zhang, Ji Zhao, Tong Wu, Cunlin Zhang, and X.-C. Zhang
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-23-13-17185

We report on the investigation of terahertz-to-infrared (THz-to-IR) thermal emission that relies on the excitation of surface plasmons in metal films deposited on a substrate with randomly ordered nanoscale pore arrays. The THz-to-IR radiation was observed both in the direction of laser beam propagation and the reverse direction. The intensity ratio between backward and forward radiation is exponentially dependent on the nominal thickness of the porous metal films. The findings are discussed in view of the proposed generation mechanism based on propagating surface plasmon polaritons on both air/metal and metal/substrate interfaces.

© 2015 Optical Society of America

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Abstract-Terahertz wave absorption via femtosecond laser-filament concatenation

Ji Zhao ; LiangLiang Zhang ; Tong Wu ; XiaoYan Xu ; CunLin Zhang ; YueJin Zhao

http://opticalengineering.spiedigitallibrary.org/article.aspx?articleid=2272700

Ji Zhao, YueJin Zhao

Beijing Institute of Technology, School of Optoelectronics, Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology, Room 6014, Optoelectronics Building, South Street of Zhongguancun, Beijing 100081, China

LiangLiang Zhang, Tong Wu, XiaoYan Xu, CunLin Zhang

Capital Normal University, Ministry of Education, Beijing Key Laboratory for Terahertz Spectroscopy and Imaging, Key Laboratory of Terahertz Optoelectronics, Beijing 100048, China

Opt. Eng. 54(4), 046104 (Apr 09, 2015). doi:10.1117/1.OE.54.4.046104

Abstract.  Terahertz (THz) emission from laser-induced air plasma is a well known and widely used phenomenon. We report that when two laser beams from the laser creating two plasma filaments interact with each other, THz absorption is observed. We believe that a change in the refractive index of the plasma causes the THz-wave absorption. The following experimental results reveal that the THz absorption becomes more pronounced with increasing pump power and that the gas species surrounding the femtosecond laser filament can also influence the THz absorption rate.

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