Fourier-transform far-infrared spectroscopic ellipsometry for standoff material identification

详细信息    查看全文

• 作者：Michele Ortolani ; Ulrich Schade
• 关键词：Infrared spectroscopy ; Ellipsometry ; Synchrotron radiation ; Terahertz range ; Explosives
• 刊名：Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
• 出版年：2010
• 出版时间：11 November 2010
• 年：2010
• 卷：623
• 期：2
• 页码：791-793
• 全文大小：373 K

文摘

The ellipsometry is an efficient method to determine the optical properties of matter. It has been largely employed with grating spectrometers in the visible, UV and near-infrared ranges for the characterization of thin films, surfaces and interfaces. In the mid- and far-infrared, where most substance-specific absorption lines are present, spectroscopic ellipsometry with Fourier-transform spectrometers is still not extended as a routine method. In particular, the lack of powerful sources in the far-infrared/terahertz range has prevented standoff application of this method. We will show that it is possible to measure the complex dielectric constant of a solid in the far-infrared and terahertz range by a reflection experiment with polarized light and ellipsometric analysis with a suitable calibration procedure. Extraction of terahertz synchrotron radiation from storage rings provides a suitable source for research-grade experiments. The optical constants determined by ellipsometry compare well with those obtained by Kramers–Kronig procedures, a method which, however, requires broader frequency range and absolute reflectance standard. We will present the case of remote spectroscopic identification of explosive materials, which is relevant for forthcoming security applications.