Accuracy and sensitivity of the thermal lens method for measuring absorption.
The effect of two lenses inserted in an optical resonator is studied. The modified resonance condition is given together with the stability condition and the spot sizes at the mirrors. Diagrams are given which allow the focal lengths of two lenses to be calculated from the known spot sizes at both mirrors. The effect of a third (the thermal) lens is studied and conditions for calculating its focal length by measuring the spot size at one mirror only are examined. The experimental procedure for the measurement of absorbencies by the thermal lens method is outlined. The various effects that can affect the precision of the measurement are studied, and the conditions for maximum sensitivity of the method are given.
Solimini
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Department of Electrical Engineering,University of California at Berkeley, USA.