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Treatment Devices
Published in Laurence J. Street, Introduction to Biomedical Engineering Technology, 2023
Excimer lasers use an inert gas such as argon or krypton combined with chlorine or fluorine to produce an ultraviolet laser beam. This beam can be very tightly focused and controlled, and its energy level means that tissue on which it is used vaporizes rather than burning. Excimer lasers are used to reshape the cornea of patients to correct their vision; by vaporizing specific areas, the cornea is deformed in such a way as to change the focus of the eye, reducing or eliminating the need for corrective lenses.
Thermo-Electrical Non-Traditional Machining Operations and Machine Tools
Published in Helmi Youssef, Hassan El-Hofy, Non-Traditional and Advanced Machining Technologies, 2020
Excimer lasers: Excimer lasers are a family of pulsed lasers operating in the ultraviolet (UV) region of the spectrum. Excimer is an acronym for “excited dimmer.” The beam is generated due to fast electrical discharges in a mixture of high-pressure dual gas, composed of one of the halogen gas group (F, H, Cl) and another from the rare gas group (Kr, Ar, Xe). The wavelength of the excimer laser attains a value from 157 to 351 nm, depending on the dual gas combination. Excimer lasers have low power output, so they remove the material photolithically, and have a remarkable application in machining of plastics and micromachining as previously mentioned. The main characteristics of important industrial lasers are given in Table 4.4.
Chemical vapour deposition of ultrafine particles
Published in Kwang Leong Choy, Chemical Vapour Deposition (CVD), 2019
The wavelength of the laser can range from the mid infrared to the ultraviolet region, i.e., excimer laser of different UV wavelengths such as 193 nm. The laser-ablation mechanism is illustrated in Figure 2.8. The material absorbs the laser light and forms the melt, which propagates into the remaining solid. The melt then absorbs the laser energy and evaporates. The vaporisation continues to form the plume which absorbs the laser, leading to the formation of a plasma. The plume will expand away from the interaction volume, the target would cool and become solid after cessation of laser pulse [20].
Laser processing of glass fiber reinforced composite material: a review
Published in Australian Journal of Mechanical Engineering, 2019
Vineeta Bhaskar, Dhiraj Kumar, K. K. Singh
A fibre laser is a laser whose active gain medium is an optical fibre doped with rare earth elements, such as Erbium, Neodymium and Ytterbium. Fibre lasers, mostly incorporated in the material processing applications, such as marking, engraving, cutting. Excimer lasers are pulsed gas lasers using a mixture of rare gas and halogen gas as the active medium. The excimer lasers operate primarily in the UV region in the mixture of rare gases (argon, krypton or xenon) with halide molecules (chlorine or fluorine). The lasers typically produce short pulses of peak power 10–20 MW with a repetition rate of up to 1000 pulses per second.
Use of lasers in minimally invasive spine surgery
Published in Expert Review of Medical Devices, 2018
Excimer laser is a pulsed gas laser that emits light with wavelengths between 157 and 351 nm. The most commonly used wavelength is 308 nm, emitted by XeCL excimer laser. As the ablation effect proceeds very rapidly, there are virtually no thermal side effects. Hence, excimer laser is mainly used in ophthalmology and angiology [21–23]. However, it has some critical disadvantages such as carcinogenic and mutagenic potential, high costs, and low radiation power, which makes the ablation process time-consuming. Therefore, it has been rarely used in spine surgery.
All-optical tunable dual Fano resonance in nonlinear metamaterials in optical communication range
Published in Journal of Modern Optics, 2018
Yi Zhou, Xiaoyong Hu, Chong Li, Hong Yang, Qihuang Gong
The 100 nm-thick nano-Au:BaSrTiO3 nanocomposite was fabricated using a laser molecular beam epitaxy growth system (Model LMBE 450, SKY Company, China), through excitation of a BaSrTiO3 target that was covered with a gold bar. We used a laser beam from an excimer laser system (Model ComPexPro 205, Coherent, USA) as the excitation light source, with an operating wavelength of 248 nm, a pulse width of 25 ns, a pulse repetition rate of 5 Hz and energy of 250 mJ/pulse. The growth process was conducted under a high-purity oxygen atmosphere at a pressure of 10 Pa during a 30 min laser deposition period. After deposition, an annealing process was performed with the oxygen pressure raised to 2000 Pa and maintained for 15 min to prevent loss of oxygen from the polycrystalline BaSrTiO3 film. The silicon substrate temperature was maintained at 550 °C throughout the entire process. The gold nanoparticle doping concentration in the matrix of the polycrystalline BaSrTiO3 film was 7%. We then used an electron-beam lithography system (Model Raith 150, Raith Co., Germany) along with the laser molecular beam epitaxy growth system to prepare the periodic patterns of the metamaterial. Finally, we used a spin-coating method to apply the multilayer-WS2 microsheet cover layer to the upper surface of the metamaterial. The single resonant unit of the metamaterial is composed of a square lattice that forms an asymmetrically split ring, consisting of a straight gold nanocuboid and a U-shaped gold nanocuboid, where both nanocuboids have thicknesses of 50 nm, as shown in Figure 1(a). The length and width of the straight gold nanocuboid were 595 nm and 80 nm, respectively, as shown in Figure 1(b). The outer and inner widths of the U-shaped gold structure were 595 nm and 435 nm, respectively. The U-shaped gold structure was also 340 nm long. A scanning electron microscopy (SEM) image of the periodic square lattice arrays of asymmetrically split rings is shown on the left side of Figure 1(c). The lattice constant was 765 nm, and the length and width of the patterned area were both approximately 200 μm. The right side of Figure 1(c) shows a high-magnification SEM image that indicates that the nano-Au:BaSrTiO3 film takes on a polycrystalline configuration with several wrinkles that were caused by the annealing process. The multilayer WS2 microsheets are shown in Figure 1(d). A 52°-inclined SEM image (Figure 1(e)) was acquired to measure the thickness of the multilayer WS2 microsheets; this thickness was approximately 157 nm.