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.
Vol. 8, Iss. 10 Virtual Journal for Biomedical Optics
Aristides Marcano, Isaac Basaldua, Aaron Villette, Raymond Edziah, Jinjie Liu, Omar Ziane, and Noureddine Melikechi, "Photothermal Lens Spectrometry Measurements in Highly Turbid Media," Appl. Spectrosc. 67, 1013-1018 (2013)