title: Thermooptic-based differential measurements of weak solute absorptions with an interferometer.
abstract: An interferometric method of measuring small differences between weak optical absorptions of solutions has been developed using the thermooptic effect. To record the small changes in optical path length ~lambda/200 due to heating, it was necessary to stabilize the fringe pattern with respect to slow thermal drift using a galvanometer-driven compensator plate controlled by a closed feedback loop. Fringe shifts from background absorptions were nulled out to better than 1 part in 400, permitting the measurement of differences in absorptions between two solutions that were l/100th of background. Using laser powers of 100 mW, absorptions approximately 5 x 10(-6) cm(-1) (base e) could be measured with CC1(4) solutions.
authors.affiliation: University of California, Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, New Mexico 87545, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Cremers
authors.forename: R A
authors.initials: RA
authors.lastname: Keller