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1 July 1998 Nonlinear absorption of photons in biological molecules: initial studies of melanin
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Proceedings Volume 3245, Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems VIII; (1998) https://doi.org/10.1117/12.312320
Event: BiOS '98 International Biomedical Optics Symposium, 1998, San Jose, CA, United States
Abstract
Based on the mechanisms of sequential two-photon absorption in biological molecules, a theoretical model is proposed for the absorption of light in melanin. To test this model, melanin samples were studied using the collinear photothermal deflection spectroscopy (PDS), with an He-Ne laser and an Argon-Krypton ion laser to provide two simultaneously exciting wavelengths. It is found that melanin samples have a strong decay in amplitude of the photothermal signal, in contrast to a reference India ink whose photothermal signal is stable. The power dependence of the amplitude of the photothermal signal is also found to exhibit a departure from linearity at higher power densities for a melanin sample. Simultaneous exposure of the same sample to He-Ne and Argon-Krypton ion laser irradiation produces a signal which is significantly less than that expected from the sum of the signals obtained from using each laser alone. These results are explained with a modification of the sequential two-photon absorption process, which involves a conversion of the photon energy to a non- thermal form such as photochemical energy.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Yue Han, Joseph S. Rosenshein, Zhouling Wu, Qiang Zhao, Tian Li Yang, Marshall Thomsen, and Wen Ye "Nonlinear absorption of photons in biological molecules: initial studies of melanin", Proc. SPIE 3245, Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems VIII, (1 July 1998); https://doi.org/10.1117/12.312320
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