Experimental instrument for observing angle- and frequency-scanned attenuated total reflection spectra

Abstract

An attenuated total reflection (ATR) instrument for the observation of angle- and frequency-scanned ATR spectra has been constructed. Light characterized by various wave vectors and dispersed into a spectrum has been detected by a charge coupled device camera after reflection from a rotating mirror and a diffraction grating. Two elliptic mirrors and a prism-sample unit have been set between the rotating mirror and the diffraction grating for the purpose of controlling the light path. The images obtained have been analyzed by a digital image processing system so that angle-scanned ATR signals are obtained for various wavelengths (500–800 nm). The time required to acquire one image has been 0.7 s in the present system. The dependence of the dielectric constant of a Ag film on wavelength is given here as an example measured by our system.

Theory of Attenuated Total Reflection Including Effects of Roughness

“…Attenuated total reflection (ATR) in the Kretschmann 5) and Otto 6) configurations is a measurement technique widely used for characterizing metallic samples, i.e., for determining their optical constants and/or thicknesses. [7][8][9][10][11][12][13][14][15][16][17][18] The technique uses interactions between light propagating in three-dimensional space (free light) and SPP, which are electromagnetic waves propagating along the sample surface but not in its normal direction, i.e., electromagnetic waves confined at the surface. 19) SPP are fundamentally nonradiative at the flat surface, i.e., SPP do not interact with free light when the surface is flat, because the wavevector of SPP is larger than the wavevector of free light at the same frequency.…”