Fiber-optic evanescent-wave spectroscopy (FEWS) is a novel method for measuring the absorption spectra of samples in contact with a segment of an optical fiber that serves as a sensing element. We used a cylindrical IR-transmitting AgClBr fiber whose central section, of length <i>L</i> , was flattened to a thickness <i>d</i> . This section was used as the FEWS sensing element. Our theoretical work predicted that the signals obtained in FEWS measurements should be linearly dependent on <i>L</i> and inversely proportional to <i>d</i> . Decreasing the thickness can significantly increase its sensitivity of the sensor. These theoretical results were verified experimentally by measurements of methanol and water.
© 2003 Optical Society of America
Y. Raichlin, L. Fel, and A. Katzir, "Evanescent-wave infrared spectroscopy with flattened fibers as sensing elements," Opt. Lett. 28, 2297-2299 (2003)