8 October 2004 Fluorescence from structure in human fingernail formed by use of a focused near-infrared femtosecond laser pulse
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Proceedings Volume 5662, Fifth International Symposium on Laser Precision Microfabrication; (2004) https://doi.org/10.1117/12.596614
Event: Fifth International Symposium on Laser Precision Microfabrication, 2004, Nara, Japan
Abstract
A shape of a structural change inside human fingernail produced by a focused femtosecond laser pulse drastically changes depending on the irradiated pulse energy. The structural changes are observed as a dark region by a microscope with transmitted illumination. When the energy is close to the threshold for producing the structural change, it had a linear shape, and at higher energy, it had conical shape. We observed a phenomenon of increase of fluorescence intensity at the structural changes. The fluorescence intensity is higher than its surrounding auto-fluorescence of a fingernail. The spectrum of the increased fluorescence coincided with the auto-fluorescence spectra of a fingernail and a pure keratin. The increase of fluorescence intensity was also observed with the fingernail heated by a drying oven. It is suggested that the fluorescence increase of the structural change is most likely caused by locally heating caused by femtosecond laser pulse irradiation. We demonstrate the fluorescence increase of the structure is useful to read out three-dimensionally recorded data inside human fingernail. Furthermore, we demonstrate the fluorescence can be observed over a half year.
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Akihiro Takita, Hirotsugu Yamamoto, Yoshio Hayasaki, Nobuo Nishida, Hiroaki Misawa, "Fluorescence from structure in human fingernail formed by use of a focused near-infrared femtosecond laser pulse", Proc. SPIE 5662, Fifth International Symposium on Laser Precision Microfabrication, (8 October 2004); doi: 10.1117/12.596614; https://doi.org/10.1117/12.596614
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