Abstract-Quantification of triglyceride levels in fresh human blood by terahertz time-domain spectroscopy

 

Dan Wang, Yu Zhang, Juan Han, Xiao Li, Xiaofeng Chen, Tianzhu Qiu,  Hua Chen, 

https://www.nature.com/articles/s41598-021-92656-4

We conducted a pilot clinical study to investigate ex vivo fresh human blood from 93 patients with coronary heart disease (CHD). The results indicated that terahertz (THz) time-domain spectroscopy (TDS) can be used to quantify triglyceride (TG) levels in human blood. Based on the TG concentrations and corresponding THz absorption coefficients, the Pearson correlation analysis demonstrated that the THz absorption coefficients have a significant negative linear correlation with TG concentration. Comparisons between the THz measurements at 0.2 THz and an automatic biochemical analyzer were performed using an additional 20 blood samples, and the results confirmed that the relative error was less than 15%. Our ex vivo human blood study indicates that the THz technique can be used to assess blood TG levels in clinical diagnostic practice.

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-Experimental results on the tunable superradiate THz radiation from the undulator in Tsinghua University beamline

Chuanxiang Tang, Wenhui Huang, Xiaolu Su,  Dan Wang, Qili Tian, Yifan Liang,  Lujia Niu, Lixin Yan, Yingchao Du,
http://ieeexplore.ieee.org/document/8067241/

We report the first operation of a widely-tunable 8-period undulator at terahertz (THz) frequencies in the Tsinghua University beamline. We observed the coherent undulator radiation from sub-picosecond electron bunches of 30MeV. The measured radiation curve shows clearly that the radiation energy is proportional to the charge square, and the THz frequency can be changed from 0.4 THz to 10 THz with narrow-band spectrums. Our results demonstrate a high power and tunable coherent THz source, which could be useful for many applications in the future.

Abstract-Phase control with two-beam interferometry method in a terahertz dielectric wakefield accelerator

 Dan Wang, Xiaolu Su, Lixin Yan,   YingChao Du, Qili Tian, Yifan Liang, Lujia Niu,   Wenhui Huang, Wei Gai, Chuanxiang Tang, Sergey Antipov,

http://aip.scitation.org/doi/abs/10.1063/1.4999959

High-gradient, beam-driven wakefield acceleration in THz structures is a promising technology for future free electron lasers and colliders. In this scheme, the main beam is accelerated by the wakefield of the high current drive beam. The time separation between the main and drive beams has to be chosen carefully to ensure that the main beam is in an accelerating phase of the drive's wakefield. THz accelerating structures provide high gradient acceleration due to their small apertures, but their phase control is difficult due to the picosecond-scale period. Here, we report on a wakefield acceleration experiment in a 460 GHz dielectric wakefield accelerator (DWA). The optimum phase of the main beam during the experiment is determined with a two-beam wakefield interferometry (TBI) measurement. This is performed without the measurement of the main and drive beam bunch lengths or their separation. In TBI, the interference of the wakefields produced by the drive and main beams is measured with an integrating THz detector. The TBI signal, as a function of separation between the drive and main beams, exhibits a minimum due to destructive interference of these wakefields, which corresponds to maximum acceleration of the main beam as is confirmed by the energy spectrometer measurement. The maximum energy gain of 0.8 MeV and maximum energy loss of 1.2 MeV for the main beam have been measured, which agrees well with theoretical predictions.