Abstract-Enhance terahertz radiation and its polarization- control with two paralleled filaments pumped by two-color femtosecond laser fields

 

Qiying Song, Xinming Yuan, Saisai Hu, Jiefeng Huang, Haizhe Zhong, Qinggang Lin, Honggeng Wang, Xiaowei Lu, Maijie Zheng, Yi Cai, Xuanke Zeng,  Shixiang Xu, 

 (a) Schematic diagram of the experimental apparatus. DWP: zero-order dual-wavelength wave plate (1/2 wave for 800 nm and full wave for 400 nm); HWP1,2,3: half-wave plate of fundamental wave; QWP: quarter-wave plate of fundamental wave; α-BBO: alpha-barium borate crystal; β-BBO: beta-barium borate crystal; BS1, BS2: beam splitters; PM: parabolic mirror; Spec: spectrometer; DS: delay stage; the THz detector system contains a pair of PMs, silicon wafer, Teflon plate and Golay cell. (b) The measured power of THz radiation as function of the power of a two-color laser field with different focal length.

https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-29-14-22659&id=452999

We present experimentally an obvious enhancement of the terahertz (THz) radiation with two paralleled filaments pumped by two-color laser fields for a full use of a high laser power, compared with single filament. By mapping the 3-dimensional electric trajectories of generated THz fields with a (111) ZnTe crystal, we observe that the total THz polarization from two filaments can be manipulated by varying the time delay between the two orthogonally polarized pumps, which agrees well with the simulations under the photocurrent model. Notably, the power and spectrum of the THz field almost keep unchanged while manipulating the ellipticity of the THz polarization, which is important for a polarization-controllable THz source.

© 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Generation of terahertz vortex pulses without any need of manipulation in the terahertz region

Qinggang Lin, Shuiqin Zheng, Qiying Song, Xuanke Zeng, Yi Cai, Ying Li, Zhenkuan Chen, Lang Zha, Xinjian Pan, and Shixiang Xu

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-44-4-887

Converting a Gaussian mode to a vortex beam is much more inconvenient in the terahertz (THz) region than in the near-infrared (NIR) region due to underdevelopment of THz components and strong THz diffraction. This Letter reports the direct generation of THz vortex pulses by optical difference-frequency between two NIR chirped pulses with different topological charges (TCs). By designing a passive and transmissive device for a collinear NIR pulse pair with conjugated TCs, we have experimentally obtained stable THz vortex pulses with a TC value of 2 or −2$-2$. The process needs no THz components and so is flexible to be realized and has promising applications in the THz field.

© 2019 Optical Society of America