Abstract-Generation of a terahertz collimated top-hat beam by using two thin diffractive phase plates

Xi Ye, Feidi Xiang, Chengwu You, Kejia Wang, Zhengang Yang, Jinsong Liu, and Shenglie Wang

Fig. 1 Configuration of THz top-hat beam shaping system with two optical elements, (a). 3D-printed refractive aspheric lenses, (b). 3D-printed diffractive phase plates.

https://www.osapublishing.org/osac/abstract.cfm?uri=osac-1-4-1341

We propose an efficient approach for shaping a terahertz (THz) Gaussian beam to a collimated top-hat beam by using two thin diffractive phase plates. The phase plates are designed based on the phase retrieve algorithm and fabricated by well-developed 3D-printing technology. The designed THz top-hat beam is experimentally realized at 0.3-THz. Both the calculated root mean square (RMS) uniformity and fraction of the total beam power of the output top-hat beam are over 80%, respectively. Additionally, the comparison between our approach and the traditional system containing of two refractive aspheric lenses is performed, showing that our beam shaping system has higher energy utilization.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-A proposed approach for detecting terahertz pulses by using double few-cycle laser pulses with opposite carrier envelope phases

Kejia Wang, Xinyang Gu, Zhenwei Zhang, Zhengang Yang, Jinsong Liu, and Shenglie Wang

https://www.osapublishing.org/col/abstract.cfm?uri=col-16-9-090401&origin=search

Previous research shows that few-cycle laser (FCL) pulses with low energy and without a bias field can be used to coherently detect terahertz (THz) pulses. As we know, it is very difficult to stabilize the carrier envelope phase (CEP) of FCL pulses, i.e., there are some random fluctuations for the CEP. Here we theoretically investigate the influence of such instability on the accuracy of THz detection. Our results show that although there is an optimum CEP for THz detection, the fluctuations of the CEP will lead to terrible thorns on the detected THz waveform. In order to solve this problem, we propose an approach using two few-cycle laser pulses with opposite CEPs, i.e., their CEPs are differed by π.

© 2018 Chinese Laser Press

Abstract-Oscillation effect in frequency domain current from a photoconductive antenna via double-probe-pulse terahertz detection technique

Qi Jin, 

Jinsong Liu, 

Kejia Wang, 

Zhengang Yang, 

Shenglie Wang, 

Kefei Ye

http://link.springer.com/article/10.1007/s12200-015-0491-1

Via constructing a special terahertz time domain spectroscopy (THz-TDS) system in which two femtosecond (fs) laser pulses were used as probe pulses to excite a photoconductive (PC) THz detector, the time behavior of the current from the detector was measured. The corresponding theoretical analysis was performed by a well-known equivalent-circuit model. When the time domain current was transformed to frequency domain, an oscillation effect was observed. The oscillation frequency was decided by the time delay between the two probe pulses. The number of the extrema in the frequency domain current curve was proportion to the pulse interval in 0.1–2 THz. A method to measure the interval of fs laser pulses was proposed. It is important for applications of fs laser pulses or train.