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Ablation
Published in John G Webster, Minimally Invasive Medical Technology, 2016
Some of the ongoing researches on laser ablation are: Laser angioplasty. The use of lasers to ablate plaque in coronary vessels has been a major challenge in laser medicine. There are many disparate approaches to this complex problem, involving different lasers (argon-ion, excimer, excimer-pumped dye, holmium: CW or pulsed), different delivery systems (single or multiple optical fibers, laser-heated metal tips, balloon catheters with laser heating) and different control and guidance methods (optical or ultrasonic imaging, fluorescence spectroscopy and imaging) (Parrish and Wilson 1991).Reshaping the cornea. This is done using 193 nm ArF excimer laser ablation in order to correct refractive abnormalities of the eye. This represents a medical procedure that depends critically on the ability of the laser to deliver controlled energy with good precision.Ultrashort pulsed laser. Capitalizing on the evolving technology of ultrashort pulse lasers could result in many advantages for biomedical applications. The major advantages of the ultrashort pulse laser (USPL) tissue ablation method are: efficient ablation due to the small input of laser energy per ablated volume of tissue and the resulting decrease of energy density needed to ablate material;the ablation threshold and rate are less dependent on tissue type and condition;high precision in ablation depth is achievable because only a small amount of tissue is ablated per pulse;low acoustical noise level (as compared to acoustical noise produced by other laser systems);minimized pain due to localization of energy deposition and damage.
Assessing the dynamic characteristics of a femtosecond laser micro plasma expansion process with an optical fiber sensing probe
Published in Khaled Habib, Elfed Lewis, Frontier Research and Innovation in Optoelectronics Technology and Industry, 2018
The diversity of phenomena that arise during the development of the interaction between lasers and materials inducing plasma has promoted research within this discipline in recent years (Eliezer, 2002). A significant amount of laser plasma research has involved the characterization of the transient response of laser-generated plasma, primarily associated with the ablation of target materials using short-pulse, high peak-power lasers (Bulgakova et al., 2000; Kabashin et al., 1998). Laser plasma research has found a wide range of applications. The study of laser plasma dynamic characteristics provides a new development direction for laser shock strengthening processing, laser shock forming, laser cleaning, laser-induced fusion, laser propulsion, laser medicine and other fields. At present, a series of researches have been carried out, both at home and abroad, into the dynamic characteristics of the laser plasma expansion process. These researches have especially made great achievements in the theoretical study of the dynamic characteristics of nanosecond-pulsed laser plasma expansion. The simulations by the existing nanosecond or longer-pulse laser ablation target material are mostly based on the classical theory of heat transfer. The establishing of a dynamic model of laser ablation plasma plume steady expansion was mainly through the related research into the transmission of pulse laser (Bogaerts et al., 2011). On the femtosecond scale, nanosecond and long-pulse laser ablation model is no longer applicable (Lv et al., 2009). In order to obtain the dynamic characteristics of the plasma expansion process induced by femtosecond laser ablation target material, laser-induced plasma diagnostic techniques are used in experimental research. Garnov et al. used over-speed spectroscopy to observe the process of plasma formation, progress and ionization at the early stage (Garnov et al., 2009). Liu et al. researched the influence of liquid environments on the femtosecond laser ablation of silicon (Liu et al., 2010). Gao et al. studied the plasma space and time-resolved emission spectra by the femtosecond-pulse laser ablation silicon (111). Gao et al. summarized the evolution of plasma plume expansion space emission wavelength shift and spectral intensity process (Gao et al., 2011). Odachi et al. studied the work on the ablation of crystalline silicon by femtosecond laser pulses in air and vacuum (Odachi et al., 2013). However, these techniques are mainly concerned on molecular spectroscopy. They cannot comprehensively monitor the dynamic characteristics of the plasma expansion process.
Optimization of diode-pumped doubly QML laser with neodymium-doped vanadate crystals at 1.34 μm
Published in Journal of Modern Optics, 2018
Ultra-short pulses generated by a Q-switched and mode-locked (QML) laser with high pulse energy and peak power have attracted the attention of many researchers because of their wide range of applications in photo-electronic devices, fibre communication, laser medicine, etc. V3+:YAG crystals have been increasingly used in QML operation due to their high damage threshold, short absorption recovery time (5 ns), high ground-state absorption cross-section, and low residual absorption at 1.34 μm. Agnesi, etc. reported a diode-pumped Nd:YVO4 QML laser with V3+:YAG as a passive modulator (1). Yang, etc. demonstrated a passive QML Nd:GdVO4/V3+:YAG laser at 1.34 μm, and H. Huang, etc. realized a passive QML Nd:Gd0.5Y0.5VO4 laser at 1.34 μm (2,3). However, the pulses obtained in QML lasers with V3+:YAG exhibit two kinds of repetition rate, which causes poor stability and limits their applications. The dual-loss modulated technique has been used in QML lasers at 1.06 μm to generate pulses with high stability and peak power (4–6). In doubly QML lasers, an active modulator, such as an acoustic-optic modulator (AOM) or electro-optic modulator, is used to control the repetition rate of the Q-switched envelope, whereas the repetition rate of the mode-locked pulses depends on the active-passive dual-loss modulation. However, the dual-loss modulated QML laser at 1.34 μm has not been systematically analysed to the best of our knowledge.