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Use of gases to sense pulsed THz waves

Research Achievements

Use of gases to sense pulsed THz waves

Two RPI IGERT trainees, Ms. Xiaofei Lu (Physics) and Mr. Nick Karpowicz (Physics), demonstrated the use of gases to sense pulsed THz waves. They used laser-induced air plasma as a broadband terahertz sensor, covering the whole THz spectrum. Unlike solid state emitters and sensors (such as semiconductors or electro-optic crystals), which are commonly used in terahertz time-domain spectroscopy, gases have no phonon resonances or reflection echoes, enabling broadband terahertz spectroscopy free of instrumental artifacts. THz detection using a gaseous medium is governed by a third-order nonlinear process: generating second harmonic photons when mixing one THz photon and two fundamental photons together. Through their investigations of over 20 gaseous species, n-butane has been demonstrated as a broadband, efficient, gas sensor with two orders magnitude enhancement of dynamic range. The work was published in the J. of Optical Society in 2009.