Abstract-Qualitative and quantitative analysis of terahertz gas-phase spectroscopy using independent component analysis

Zhijie Li, Nick Rothbart, Xiaojiao Deng, Hua Geng, Xiaoping Zheng, Philipp Neumaier, Heinz-Wilhelm Hübers, 



https://www.sciencedirect.com/science/article/abs/pii/S0169743920300307

This study aims at the qualitative and quantitative analysis of the absorption spectra of gas mixtures measured around 245 GHz. Gas-phase spectra of several volatile organic compounds were measured at different pressures. Based on these spectral data, the independent component analysis (ICA) was applied to recover the components’ spectra and predict their relative concentrations. It is demonstrated that the ICA method is a promising tool to decompose the mixture spectra contributing to high-accuracy qualitative and quantitative analysis of terahertz gas-phase spectroscopy.

Abstract-Analysis of Human Breath by Millimeter-Wave/Terahertz Spectroscopy

Nick Rothbart,  Olaf Holz, Rembert Koczulla, Klaus Schmalz,  Heinz-Wilhelm Hübers

https://www.mdpi.com/1424-8220/19/12/2719/pdf

Breath gas analysis is a promising tool for medical research and diagnosis. A particularly powerful technological approach is millimeter-wave/terahertz (mmW/THz) spectroscopy, because it is a very sensitive and highly selective technique. In addition, it offers the potential for compact and affordable sensing systems for wide use. In this work, we demonstrate the capability of a mmW/THz spectrometer for breath analysis. Samples from three volunteers and a sample from ambient air were analyzed with respect to 31 different molecular species. High-resolution absorption spectra were measured by scanning two absorption lines from each species. Out of the 31, a total of 21 species were detected. The results demonstrate the potential of mmW/THz spectroscopy for breath analysis.

Abstract- Gas Spectroscopy System for Breath Analysis at mm-wave/THz Using SiGe BiCMOS Circuits

 Klaus Schmalz,   Nick Rothbart ,  Philipp F.-X. Neumaier,  Johannes Borngräber,   Heinz-Wilhelm Hübers,  Dietmar Kissinger

http://ieeexplore.ieee.org/document/7836317/

The unique fingerprint spectra of volatile organic compounds for breath analysis and toxic industrial chemicals make an mm-wave (mmW)/THz gas sensor very specific and sensitive. This paper reviews and updates results of our recent work on sensor systems for gas spectroscopy based on integrated transmitter (TX) and receiver (RX), which are developed and fabricated in IHP's 0.13 μm SiGe BiCMOS technology. In this paper, we present an mmW/THz spectroscopic system including a folded gas absorption cell of 1.9 m length between the TX and RX modules. We discuss the results and specifications of our sensor system based on integrated TX and RX. We demonstrate TXs and RXs with integrated antennas for spectroscopy at 238-252 GHz and 494-500 GHz using integer-N phase-locked loops (PLLs). We present a compact system by using fractional-N PLLs allowing frequency ramps for the TX and RX, and for TX with superimposed frequency shift keying or reference frequency modulation. In another configuration, the voltage controlled oscillators of the TX and RX local oscillator are tuned directly without PLLs by applying external voltages. Further developments of our system are aimed at realizing an even wider frequency span by switching between frequency bands, and to use a more compact gas absorption cell.

Abstract-High-spectral-resolution terahertz imaging with a quantum-cascade laser

Till Hagelschuer, Nick Rothbart, Heiko Richter, Martin Wienold, Lutz Schrottke, Holger T. Grahn, and Heinz-Wilhelm Hübers

https://www.osapublishing.org/oe/abstract.cfm?URI=oe-24-13-13839

We report on a high-spectral-resolution terahertz imaging system operating with a multi-mode quantum-cascade laser (QCL), a fast scanning mirror, and a sensitive Ge:Ga detector. By tuning the frequency of the QCL, several spectra can be recorded in 1.5 s during the scan through a gas cell filled with methanol (CH3OH). These experiments yield information about the local absorption and the linewidth. Measurements with a faster frame rate of up to 3 Hz allow for the dynamic observation of CH3OH gas leaking from a terahertz-transparent tube into the evacuated cell. In addition to the relative absorption, the local pressure is mapped by exploiting the effect of pressure broadening.

© 2016 Optical Society of America

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Abstract-Granular Structure Determined by Terahertz Scattering

Philip Born, Nick Rothbart, Matthias Sperl, Heinz-Wilhelm Hübers
 (Submitted on 23 Dec 2013)
http://arxiv-web3.library.cornell.edu/abs/1312.6519

 Light-scattering in the terahertz region is demonstrated for granular matter. A quantum-cascade laser is used in a benchtop setup to determine the angle-dependent scattering of spherical grains as well as coffee powder and sugar grains. For the interpretation of the form factors for the scattering from single particles one has to go beyond the usual Rayleigh-Gans-Debye theory and apply calculations within Mie theory. In addition to single scattering also collective correlations can be identified and extracted as a static structure factor.