Abstract-A 300 THz tabletop radar range system with sub-micron distance accuracy

Pierre-Alexandre Blanche, Mark Neifeld, Mingguang Tuo, Hao Xin, N. Peyghambarian,

https://www.nature.com/articles/s41598-018-32846-9

We are presenting a compact radar range system with a scale factor of 105. Replacing the radio frequency (RF) by optical wavelength (300 THz), the system easily fit on a tabletop. We used interferometric time-of-flight to reproduce radar ranging measurements. Sub-micron range accuracy was achieved with a 100 fs laser pulse, which correspond to 3 cm for a s-band (3 GHz) radar. We demonstrated the system potential on a simple target, and compared the results with radio frequency measurement using a vector network analyzer. We also present measurement with a more realistic model, a 3D printed reproduction of the USS Arizona battleship, for which a 3D model is extracted from the ranging data. Together with our previous demonstration of radar cross section measurement with a similar system, this report further validates our proposal to use optics to simulate radar properties of complex radio frequency systems.

Abstract-Contribution assessment of antenna structure and in-gap photocurrent in terahertz radiation of photoconductive antenna

Jitao Zhang,  Mingguang Tuo, Min Liang,  Xiong Wang,  Hao Xin

https://aip.scitation.org/doi/abs/10.1063/1.5038341

Photoconductive antenna (PCA) is one of the most widely used terahertz (THz) devices nowadays. Although PCAs have been extensively studied through both theoretical analysis and device design, there still lacks a common agreement upon the mechanism of THz radiation. One of the central questions is how to distinguish and assess the contribution of the antenna structure and in-gap photocurrent to the overall radiation of a PCA. In this work, a three-dimensional full-wave model was first used to quantify the overall far-field radiation of PCAs. The commercial solver (i.e., HFSS) and the Hertzian dipole approximation method were then applied to quantify the far-field radiation solely from the antenna structure and in-gap photocurrent, respectively. The contribution of the antenna structure and in-gap photocurrent can therefore be distinguished by comparing the simulation results among the three methods. The results suggest that, although the THz radiation originates from laser-excited photocurrent within the gap, the overall THz radiation of a PCA is predominated by the antenna structure. As a validation, the cancellation effect was predicated by numerical simulation of coplanar stripline PCA and confirmed with experiment using butterfly shaped stripline PCA. The presented work uncovers the details of the underlying radiation mechanism of the PCA. This could inspire PCA design that aims for engineering the radiation properties of a PCA for specific applications.

Abstract-Microfluidic Devices for Terahertz Spectroscopy of Live Cells Toward Lab-on-a-Chip Applications

Qi Tang 1

, Min Liang 1

, Yi Lu 2

, Pak Kin Wong 2

, Gerald J. Wilmink 3

, Donna D. Zhang 4

 and Hao Xin 1,* 

1 Department of Electrical and Computer Engineering, University of Arizona, Tucson, AZ 85721, USA2 Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA3 WiseWear Corporation, New York, NY 10018, USA4 College of Pharmacy, University of Arizona, Tucson, AZ 85721, USA

* Author to whom correspondence should be addressed.

http://www.mdpi.com/1424-8220/16/4/476

THz spectroscopy is an emerging technique for studying the dynamics and interactions of cells and biomolecules, but many practical challenges still remain in experimental studies. We present a prototype of simple and inexpensive cell-trapping microfluidic chip for THz spectroscopic study of live cells. Cells are transported, trapped and concentrated into the THz exposure region by applying an AC bias signal while the chip maintains a steady temperature at 37 °C by resistive heating. We conduct some preliminary experiments on E. coli and T-cell solution and compare the transmission spectra of empty channels, channels filled with aqueous media only, and channels filled with aqueous media with un-concentrated and concentrated cells.