Abstract
Clinical therapy incorporating femtosecond laser (FSL) devices is a quickly growing field in modern biomedical technology due to their precision and ability to generate therapeutic effects with substantially less laser pulse energy. FSLs have the potential to produce nonlinear optical effects such as harmonic generation (HG), especially in tissues with significant nonlinear susceptibilities such as the cornea. HG in corneal tissue has been demonstrated in nonlinear harmonic microscopy using low-power FSLs. Furthermore, the wavelength ranges of harmonic spectral emissions generated in corneal tissues are known to be phototoxic above certain intensities. We have investigated how the critical FSL parameters pulse energy, pulse repetition rate, and numerical aperture influence both second (SHG) and third harmonic generation (THG) in corneal tissue. Experimental results demonstrated corresponding increases in HG intensity with increasing repetition rate and numerical aperture. HG duration decreased with increasing repetition rate and pulse energy. The data also demonstrated a significant difference in HG between FSL parameters representing the two most common classes of FSL therapeutic devices.
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The mention of commercial products, their sources, or their use in connection with material reported here is not to be construed as either an actual or implied endorsement of such products by the U.S. Food and Drug Administration (FDA). This article does not contain any studies with animals performed by any of the authors.
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Calhoun, W.R., Ilev, I.K. Effect of therapeutic femtosecond laser pulse energy, repetition rate, and numerical aperture on laser-induced second and third harmonic generation in corneal tissue. Lasers Med Sci 30, 1341–1346 (2015). https://doi.org/10.1007/s10103-015-1726-5
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DOI: https://doi.org/10.1007/s10103-015-1726-5