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Appl Phys Lett. 2010 Oct 18;97(16):163701.

Picosecond absorption relaxation measured with nanosecond laser photoacoustics.

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Department of Biomedical Engineering, Optical Imaging Laboratory, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri 63130, USA.


Picosecond absorption relaxation-central to many disciplines-is typically measured by ultrafast (femtosecond or picosecond) pump-probe techniques, which however are restricted to optically thin and weakly scattering materials or require artificial sample preparation. Here, we developed a reflection-mode relaxation photoacoustic microscope based on a nanosecond laser and measured picosecond absorption relaxation times. The relaxation times of oxygenated and deoxygenated hemoglobin molecules, both possessing extremely low fluorescence quantum yields, were measured at 576 nm. The added advantages in dispersion susceptibility, laser-wavelength availability, reflection sensing, and expense foster the study of natural-including strongly scattering and nonfluorescent-materials.

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