Action Mechanisms of Laser Radiation in Biological Tissues

Nanorods as Wavelength‐Selective Absorption Centers in the Visible and Near‐Infrared Regions of the Electromagnetic Spectrum

“…[8] For such applications, it is essential to design nanoparticles with enhanced absorption in the near-infrared region of the electromagnetic spectrum, [8,9] where light absorption by tissue is minimal. [10] In the case of gold nanoparticles, the surface plasmon resonance absorption in the near-infrared region of the electromagnetic spectrum can be controlled by tuning the aggregation state of the particles, as shown for the case of high concentration. [11] In contrast, the anisotropic shape of nanorods enables the tuning of their absorption characteristics [12] over a broad spectral range extending to the near-infrared.…”

Skin Laser Treatments Enhancing Transdermal Delivery of ALA

“…There is also a dependence on the optical properties of the irradiated tissue such as optical density, structure, and absorption maximum. 24 An estimation on the content of water into the skin structures can be: 80% into the dermis, 65-70% into the epidermis and 13% into the SC. 25 Water exhibits maximum absorption at 3000 nm.…”

Recent advances in infrared laser lithotripsy [Invited]

“…The temperature rise chemically decomposes and melts stones depending on their specific thermal properties. However, the absorption coefficients of different dry stone compositions have been reported to be similar at IR wavelengths [ 9 ], which is inconsistent with the wide range of ablation thresholds and ablation rates observed for different laser wavelengths and stone compositions, leading to the hypothesis that other mechanisms may contribute to stone ablation as well. For example, ablation thresholds at the Holmium:YAG wavelength of 2120 nm have been measured for all the stone compositions listed in Table 1…”

“…The Thulium fiber laser operates with two primary emission wavelengths of 1908 and 1940 nm, which more closely match a water absorption peak than that of the Holmium laser wavelength at 2100 nm [ 22 – 24 ]. As previously mentioned, absorption of IR energy by water is believed to play a major role in stone ablation, in addition to direct absorption of laser energy by the stone material, since IR absorption by dry stones are similar for different stone compositions [ 8 , 9 , 21 ]. The water absorption coefficient is µ a = 120 cm −1 for Thulium fiber laser, µ a = 62 cm −1 for Thulium:YAG laser, and µ a = 24 cm −1 for Holmium:YAG lasers ( Table 2 ).…”