The evolution of the spatial profile of a thermal lens induced by a low-power laser beam in an absorbing dye solution is directly visualized in real time using low-coherence light interferometry. Both spatial characteristics and response times of the lens are measured. Comparisons between experimental results and thermal diffusion theory are presented. The resolution of the measured refractive index in the thermal lens profile is better than 10 6. # 1999 Society of Photo-Optical Instrumentation Engineers. S0091-3286(99)00909-5 Subject terms: thermal effects; interferometry; phase measurement; high-resolution measurements. Paper 980455 received Nov. 11, 1998; revised manuscript received Mar. 22, 1999; accepted for publication Mar. 25, 1999. This paper is a revision of a paper presented at the SPIE symposia "Optical Technology in Fluid, Thermal and Combustion Flow II1" at the SPIE Annual Meeting, July 1997, San Diego, California. The paper presented there appears (unrefereed) in Proc. SPIE 3172.
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