A comparison of a first-order thermal lensing model to a closed aperture Z-scan for the propagation of light in ocular media

摘要

The phenomenon of thermal lensing was investigated in water using a Z-scan method and corresponding first-order mathematical models. Data from first-order thermal lensing models and ABCD beam propagation methods were used to simulate the non-linear absorption of water held in a thin sample cuvette for a Z-scan optical set up of CW cases at 1313 nm. The single beam closed aperture Z-scan was then used to determine the non-linear absorption at 1313 nm for water in 10 mm and 2 mm cuvettes at 48.00, 16.80, 9.80 and 2.83 mW then compared to the first-order model data. The results from the closed aperture Z-scan were also used to back calculate the spot size in the far field for comparison to the model's prediction of the beam's temporal response. Experimental Z-scan data were found not to correlate strongly with our first-order model suggesting the need for higher order models to successfully predict spot size in absorbing media inside the Rayleigh range.