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Photothermal Lens Spectrometry Measurements in Highly Turbid Media

Volume 67, Number 9 (Sept. 2013) Page 1013-1018

ARISTIDES MARCANO,* ISAAC BASALDUA, AARON VILLETTE, RAYMOND EDZIAH, JINJIE LIU, OMAR ZIANE, and NOUREDDINE MELIKECHI


We measured the photothermal lens signal in samples exhibiting high turbidity using a pump-probe scheme. We show that the photothermal lens signal properties remain nearly unchanged up to values of turbidity of 6 cm−1 despite the signal reduction due to the decrease of excitation power associated to turbidity losses. The signal starts decreasing abruptly for values of turbidity larger than 6 cm−1. Multiple light scattering yields a reduction of the temperature gradients, which results in a decrease of the effective signal. However, the signal-to-noise ratio remains above 50 for turbidity values of 9 cm−1, which corresponds to a reduction of light transmission by more than four orders of magnitude. We report on the detection of the photothermal lens signal through a 2 mm layer of organic tissue with a signal-to-noise ratio of about 500. This technique appears promising for imaging applications in organic samples, which usually exhibit high turbidity for visible and near-infrared light.



Index Headings: Thermal lens spectrometry; Scattering effect; Photothermal effects; Absorption spectroscopy..