New thermooptical measurement method and a comparison with other methods

Chen-Ming Hu, J. R. Whinnery

Research output: Contribution to journalArticlepeer-review

281 Scopus citations


A simple and sensitive method of measuring the thermally induced index changes arising from absorption of a laser beam in a low-loss material is described. The sample is placed outside the laser cavity, but at the position of minimum radius of curvature of the wavefront, which is a confocal distance behind the waist. It is estimated that the method is sensitive enough to measure absorption coefficients of the order of 5 × 10-6 cm-1 and it is shown experimentally to have good accuracy on low-loss materials. A detailed comparison of sensitivity and accuracy estimates is given for the various published thermal-lens methods for measuring low absorption coefficients. Although the method is illustrated for the thermal effect, it is applicable to other nonlinear index changes induced by laser beams.

Original languageEnglish
Pages (from-to)72-79
Number of pages8
JournalApplied Optics
Issue number1
StatePublished - 1 Jan 1973


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