Abstract-Towards realization of quantitative atmospheric and industrial gas sensing using THz wave electronics

Aniket Tekawade, Timothy E. Rice, Matthew A. Oehlschlaeger, Muhammad Waleed Mansha,  Kefei Wu, Mona M. Hella, Ingrid Wilke

https://link.springer.com/article/10.1007/s00340-018-6974-1

The potential of THz wave electronics for miniaturized non-intrusive sensors for atmospheric, environmental, and industrial gases is explored. A THz wave spectrometer is developed using a radio-frequency multiplier source and a Schottky-diode detector. Spectral absorption measurements were made in a gas cell within a frequency range of 220–330 GHz at room temperature and subatmospheric pressures. Measurements are reported for pure acetonitrile (CH3CN), methanol (CH3OH), and ethanol (C2H5OH) vapors at 5 and 10 Torr and for methanol dilute in the air (0.75–3.0 mol%) at a pressure of 500 Torr. An absorbance noise floor of 10−3was achieved for a single 10 s scan of the 220–330 GHz frequency domain. Measured absorption spectra for methanol/air agree well at collisional-broadened conditions with spectral simulations carried out using literature spectroscopic parameters. In contrast to the previous submillimeter wave research that has focused on spectral absorbance at extremely low pressures (mTorr), where transitions are in the Doppler limit, and the present study illustrates the applicability of THz electronics for gas sensing at pressures approaching those found in atmospheric and industrial environments.

Abstract-Optical and THz Evaluation of Components for Gas Sensing Spectroscopy in Hazardous Environments

Dan Sporea, Laura Mihai, Adelina Sporea, Daniel Ighigeanu, Daniel Neguţ

https://link.springer.com/chapter/10.1007/978-94-024-1093-8_9

In this paper, we report for the first time a comparative investigation on gamma and electron beam irradiation effects on some mid-IR materials (ZnSe, CaF2, BaF2, and sapphire) used as components in trace gas detection systems, in the 15–100 THz spectral range. Optical transmittance/reflectance measurements were performed from UV to far IR (0.2–23 μm) on both non-irradiated and irradiated samples. These investigations were complemented by THz spectroscopy and imaging tests run under the same conditions.

Abstract-Terahertz gas sensing based on a simple one-dimensional photonic crystal cavity with high-quality factors

Tao Chen, Zhanghua Han, Jianjun Liu, and Zhi Hong  »View Author Affiliations

Applied Optics, Vol. 53, Issue 16, pp. 3454-3458 (2014)
http://dx.doi.org/10.1364/AO.53.003454

http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-53-16-3454

We report in this paper terahertz gas sensing using a simple 1D photonic crystal cavity. The resonant frequencies of the cavity depend linearly on the refractive index of the ambient gas, which can then be measured by monitoring the resonance shift. Although quite easy to manufacture, this cavity exhibits high-quality factors, facilitating the realization of high sensitivity in the gas refractive index sensing. In our experiment, 6% of the change of hydrogen concentration in air, which corresponds to a refractive index change of 1.4×10−5, can be steadily detected, and different gas samples can be easily identified. Our experimental results are consistent with the theoretically calculated spectral responses of the cavity using the transfer matrix method.

© 2014 Optical Society of America