Abstract-1.4‐mJ High Energy Terahertz Radiation from Lithium Niobates

 

Baolong Zhang,  Zhenzhe Ma, Jinglong Ma,  Xiaojun Wu,  Chen Ouyang,  Deyin Kong,  Tianshu Hong,  Xuan Wang,  Peidi Yang, Liming Chen, Yutong Li, Jie Zhang, 

https://onlinelibrary.wiley.com/doi/abs/10.1002/lpor.202000295

Free‐space super‐strong terahertz (THz) electromagnetic fields offer multifaceted capabilities for reaching extreme nonlinear THz optics. However, the lack of powerful solid‐state THz sources with single pulse energy >1 mJ is impeding the proliferation of extreme THz applications. The fundamental challenge lies in hard to achieve high efficiency due to high intensity pumping caused crystal damage, linear absorption, and nonlinear distortion induced short effective interaction length, and so on. Here, through cryogenically cooling the crystals, tailoring the pump laser spectra, chirping the pump pulses, and magnifying the laser energies, 1.4‐mJ THz pulses are successfully realized in lithium niobates under the excitation of 214‐mJ femtosecond laser pulses via tilted pulse front technique. The 800 nm‐to‐THz energy conversion efficiency reaches 0.7%, and a free‐space THz peak electric and magnetic field reaches 6.3 MV cm−1 and 2.1 Tesla. Numerical simulations reproduce the experimental optimization processes. To show the capability of this super‐strong THz source, nonlinear absorption in high conductive silicon induced by strong THz electric field is demonstrated. Such a high‐energy THz source with a relatively low peak frequency is very appropriate not only for electron acceleration toward table‐top X‐ray sources but also for extreme THz science and nonlinear applications.

Abstract-Terahertz strong-field physics in light-emitting diodes for terahertz detection and imaging

Communications Physics

Chen Ouyang, Shangqing Li, Jinglong Ma, Baolong Zhang, Xiaojun Wu, Wenning Ren, Xuan Wang, Dan Wang, Zhenzhe Ma, Tianze Wang, Tianshu Hong, Peidi Yang, Zhe Cheng, Yun Zhang, Kuijuan Jin,  Yutong Li

https://www.nature.com/articles/s42005-020-00508-w

Intense terahertz (THz) electromagnetic fields have been utilized to reveal a variety of extremely nonlinear optical effects in many materials through nonperturbative driving of elementary and collective excitations. However, such nonlinear photoresponses have not yet been obeserved in light-emitting diodes (LEDs), let alone employing them as fast, cost-effective, compact, and room-temperature-operating THz detectors and cameras. Here, we report ubiquitously available LEDs exhibiting photovoltaic signals of ~0.8 V and ~2 ns response time with signal-to-noise ratios of ~1300 when being illuminated by THz field strengths ~240 kV/cm. We also demonstrated THz-LED detectors and camera prototypes. These unorthodox THz detectors exhibited high responsivities (>1 kV/W) with response time four orders of magnitude shorter than those of pyroelectric detectors. The mechanism was attributed to THz-field-induced impact ionization and Schottky contact. These findings not only help deepen our understanding of strong THz field-matter interactions but also contribute to the applications of strong-field THz diagnosis.

Abstract-Terahertz Strong-Field Physics in Light-Emitting Diodes for Terahertz Detection and Imaging

Chen Ouyang, Shangqing Li, Jinglong Ma, Baolong Zhang, Xiaojun Wu, Wenning Ren, Xuan Wang, Dan Wang, Zhenzhe Ma, Tianze Wang, Tianshu Hong, Peidi Yang, Zhe Cheng, Yun Zhang, Kuijuan Jin, Yutong Li

https://arxiv.org/abs/2007.14093

Intense terahertz (THz) electromagnetic fields have been utilized to reveal a variety of extremely nonlinear optical effects in many materials through nonperturbative driving of elementary and collective excitations. However, such nonlinear photoresponses have not yet been discovered in light-emitting diodes (LEDs), letting alone employing them as fast, cost effective,compact, and room-temperature-operating THz detectors and cameras. Here we report ubiquitously available LEDs exhibited gigantic and fast photovoltaic signals with excellent signal-to-noise ratios when being illuminated by THz field strengths >50 kV/cm. We also successfully demonstrated THz-LED detectors and camera prototypes. These unorthodox THz detectors exhibited high responsivities (>1 kV/W) with response time shorter than those of pyroelectric detectors by four orders of magnitude. The detection mechanism was attributed to THz-field-induced nonlinear impact ionization and Schottky contact. These findings not only help deepen our understanding of strong THz field-matter interactions but also greatly contribute to the applications of strong-field THz diagnosis.

Abstract-High spatial resolution diffraction diagnostics for intense terahertz sources

Shang-Qing Li, Jing-Long Ma, Xiao-Jun Wu, Bao-Long Zhang, Chen Ou-Yang, Tian-Ze Wang, Dan Wang, Xuan Wang, Yu-Tong Li

https://arxiv.org/abs/1910.05714

We propose a high resolution spatial diagnostic method via inserting a millimeter-gap grating into the collimated terahertz beam to monitor the minute variation of the terahertz beam in strong-field terahertz sources, which is difficult to be resolved in conventional terahertz imaging systems. To verify the method, we intentionally fabricate tiny variations of the terahertz beam through tuning the iris for the infrared pumping beam before the tilted pulse-front pumping (TPFP) setups. The phenomena can be well explained by the the theory based on tilted pulse front technique and terahertz diffraction. We believe our observation not only help further understand the mechanism of intense terahertz generation, but also may be useful for strong-field terahertz applications.

Abstract-Highly efficient generation of 0.2 mJ terahertz pulses in lithium niobate at room temperature with sub-50 fs chirped Ti:sapphire laser pulses

Xiao-jun Wu, Jing-long Ma, Bao-long Zhang, Shu-su Chai, Zhao-ji Fang, Chen-Yi Xia, De-yin Kong, Jin-guang Wang, Hao Liu, Chang-Qing Zhu, Xuan Wang, Cun-Jun Ruan, and Yu-Tong Li

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-6-7107#top

We demonstrate generation of 0.2 mJ terahertz (THz) pulses in lithium niobate driven by Ti:sapphire laser pulses at room temperature. Employing tilted pulse front technique, the 800 nm-to-THz energy conversion efficiency has been optimized to 0.3% through chirping the sub-50 fs pump laser pulses to overcome multi-photon absorption and to extend effective interaction length for phase matching. Our approach paves the way for mJ-level THz generation via optical rectification using existing Ti:sapphire laser systems which can deliver Joule-level pulse energy with sub-50 fs pulse duration.

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

Abstract-Demonstration of Coherent Terahertz Transition Radiation from Relativistic Laser-Solid Interactions

Guo-Qian Liao, Yu-Tong Li, Yi-Hang Zhang, Hao Liu, Xu-Lei Ge, Su Yang, Wen-Qing Wei, Xiao-Hui Yuan, Yan-Qing Deng, Bao-Jun Zhu, Zhe Zhang, Wei-Min Wang, Zheng-Ming Sheng, Li-Ming Chen, Xin Lu, Jing-Long Ma, Xuan Wang, and Jie Zhang

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.205003

Coherent transition radiation in the terahertz (THz) region with energies of sub-mJ/pulse has been demonstrated by relativistic laser-driven electron beams crossing the solid-vacuum boundary. Targets including mass-limited foils and layered metal-plastic targets are used to verify the radiation mechanism and characterize the radiation properties. Observations of THz emissions as a function of target parameters agree well with the formation-zone and diffraction model of transition radiation. Particle-in-cell simulations also well reproduce the observed characteristics of THz emissions. The present THz transition radiation enables not only a potential tabletop brilliant THz source, but also a novel noninvasive diagnostic for fast electron generation and transport in laser-plasma interactions.

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• Received 12 January 2016

DOI:http://dx.doi.org/10.1103/PhysRevLett.116.205003

Abstract-Plasmonic Nature of the Terahertz Conductivity Peak in Single-Wall Carbon Nanotubes

Qi Zhang , Erik Haroz , Zehua Jin , Lei Ren , Xuan Wang , Rolf S. Arvidson , Andreas Luttge , and Junichiro Kono
http://pubs.acs.org/doi/abs/10.1021/nl403175g?journalCode=nalefd

Plasmon resonance is expected to occur in metallic and doped semiconducting carbon nanotubes in the terahertz frequency range, but its convincing identification has so far been elusive. The origin of the terahertz conductivity peak commonly observed for carbon nanotube ensembles remains controversial. Here we present results of optical, terahertz, and DC transport measurements on highly enriched metallic and semiconducting nanotube films. A broad and strong terahertz conductivity peak appears in both types of films, whose behaviors are consistent with the plasmon resonance explanation, firmly ruling out other alternative explanations such as absorption due to curvature-induced gaps.