Achievement

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.