Optical probe for remote attenuated total reflectance measurements

Abstract

A probe for use in attentuated total reflectance measurements in spectroscopy, such as Fourier transform infrared spectroscopy, is formed of an optical waveguide element having input and output sections and a loop between the two sections. The loop has a small radius of curvature and is exposed so that it can be contacted with a sample to obtain attenuated total reflectance measurements. The input and output sections may be retained in the bore of a thin walled tube with the loop forming a tip which extends from one end of the tube. The input and output sections of the optical waveguide element may be connected by couplers to a spectrometer to receive the output beam from and provide a return beam to the spectrometer. The tightly curved surfaces of the optical waveguide element at the loop result in multiple internal reflections as the beam of radiation traverses the loop. Attenuated total reflectance interactions occur between the beam of radiation and sample material in contact with the loop, which can comprise a liquid, a gas, or relatively soft solid materials.