Abstract
We studied a method for preparing a thin optical window in the human fingernail to enable the optical monitoring of biosubstances in the nail bed. To prepare a thin optical window without injuring the nail bed, an ArF excimer laser was used to ablate the nail plate. The fluorescence induced during laser processing was measured to control ablation. The etching depth of the nail plate per pulse during ArF excimer laser ablation at a practical pulse energy density of 630 mJ/cm2 was about 0.3 μm. The result indicates that the nail plate can be accurately processed to a thickness of less than 1 μm during ArF excimer laser ablation. The ArF excimer laser-induced fluorescence spectrum of the nail bed was different from that of the nail plate. This result suggests that it may be possible to discriminate between the tissues in the nail plate and nail bed by measuring the fluorescence induced by the ablation laser. We used an ArF excimer laser to ablate the nail plate of the fluorescence model of a nail bed, and controlled ablation by measuring the laser-induced fluorescence. A thin optical window having a minimum thickness of 4 μm was made in the nail without ablation of the fluorescence model in the nail bed. This proves that it is possible to use ArF laser ablation to prepare a thin optical window in the fingernail without injuring the nail bed, the process of which is controlled by measuring the laser-induced fluorescence.
