Citation:
Jane Hodgkinson, Mark Johnson, and John P. Dakin, Photothermal Detection of Trace Optical Absorption in Water by Use of Visible-Light-Emitting Diodes, Applied Optics, 1998, Vol. 37, Issue 31, pp. 7320-7326
Abstract:
Visible light emitting diodes of three different colors have been used to detect an absorbing compound
(potassiumpermanganate) in trace quantities in aqueous solution. Photothermal absorption in a closed cell
caused deflection of a water meniscus held at a small pinhole. The displacement was monitored using
optical fiber interferometry. The technique was limited by LED emission intensities and environmental
acoustic noise, giving minimum detectable absorption coefficients of 2x10-4 cm-1 at 478 nm and 658 nm,
and 3x10-4 cm-1 at 524 nm. The magnitude and form of meniscus deflection signals were shown to be in
good agreement with theory.
