We have performed terahertz time-domain spectroscopy measurements on three types of polystyrene foam. We find that between 0.2 and 4 THz, the extinction of this material is low and that it has a remarkably low refractive index of 1.017 to 1.022 in this range, with little variation as a function of frequency. In foam produced with HCFC 142b gas (1-chloro-1,1-difluoroethane) as the blowing agent, we find an additional absorption band at 0.5 THz caused by rotational transitions in this gas. The low extinction and refractive index make polystyrene foam a very suitable material to be used as a dichroic filter that blocks the near-IR and transmits THz radiation with small losses of less than 1.5 cm−1 for frequencies of <4 THz, and as a substrate for THz imaging.
© 2002 Optical Society of America
(300.6250) Spectroscopy : Spectroscopy, condensed matter
(300.6270) Spectroscopy : Spectroscopy, far infrared
(300.6390) Spectroscopy : Spectroscopy, molecular
(320.7150) Ultrafast optics : Ultrafast spectroscopy
Guozhong Zhao, Maarten ter Mors, Tom Wenckebach, and Paul C. M. Planken, "Terahertz dielectric properties of polystyrene foam," J. Opt. Soc. Am. B 19, 1476-1479 (2002)