The layers’ thickness for different samples and parameters of laser radiation used to assist crystallization are shown in Table 1. As a laser system can deliver a wide range of pulse durations (between 0.1 and 50 ns) for LSP, the laser pulse duration directly controls the pressure pulse duration (Cottet and Boustie, 1989; Devaux et al., 1993; Gerland and Hallouin, 1994; Couturier et al., 1996). Continuous tuning of the repetition rate is standard. Further development of the proposed mechanism confirmed that Sn-induced crystallization of α-Si accelerates when laser radiation is applied to the solution [23]. Note larger scattering of in comparison with values caused by a larger statistical error of calculation. The fact that the starting temperature for structural changes in the studied samples of Si-Sn-Sn was very close to the melting point of Sn supports our recent conclusion on the physical mechanisms of Sn-induced crystallization in α-Si as the cyclic process of formation and decay of a saturated solution of Si in molten Sn [20, 21]. Note that samples #3 and #6 differed only by the range of the laser power variation. Such deviation of the simulation results from the experimental data may be explained by the influence of nonlinear optical effects, in particular by the absorption saturation in studied samples [39]. Therefore, a picosecond laser will have a much higher peak power than a longer nanosecond or millisecond pulsed laser. The partial volume of the crystalline phase changes also sharply. These experiments with sample #7 evidenced that the amorphous film degraded essentially without crystallization at irradiation intensities = (1.5–2.0) × 108 W/сm2. Dependencies of the nanocrystals size (a) and partial volume of the crystalline phase (b) on the power density of laser irradiation. V. B. Neimash, A. O. Goushcha, L. L. Fedorenko, P. Ye. Laser pulse duration Definition from Government Dictionaries & Glossaries. We are committed to sharing findings related to COVID-19 as quickly as possible. In more loosely-defined terms, it is an indicator of the amount of energy a laser pulse contains in comparison to its temporal duration, namely pulse width. Note that each point of the graphs in Figure 7 corresponds to a specific location on the sample’s surface subjected to a pulsed illumination with the laser beam of 70 um spot diameter and applying 50 um scanning step. To be considered an ultrafast laser, the pulse duration of the laser needs to be 10ps or less. In all cases below, we will assume the absence of the temperature increase in the structure prior to optical excitation as the initial condition . The initial (as-grown) Raman spectra of the samples from #1 to #6-2 contained both the α-Si and nc-Si Raman bands. In addition, applying laser radiation allowed online detection of the Raman spectra providing thereby the capabilities to monitor the temperature, partial volume, and nanocrystal sizes in nc-Si composite during its formation and showing the possibility to control efficiently the crystallization process by varying the intensity and irradiation time of laser light. Divide the energy per pulse by the pulse width (in time) and you will get the peak power. Shepelyavyi, V. V. Strelchuk, A. S. Nikolenko, M. V. Isaiev, A. G. Kuzmich, "Role of Laser Power, Wavelength, and Pulse Duration in Laser Assisted Tin-Induced Crystallization of Amorphous Silicon", Journal of Nanomaterials, vol. All larger size crystals were not readily distinguished from the monocrystalline Si in Raman spectra. The volume sources of heat in the modified (by the optical pulse action) layer are considered as the top-surface layer sources: where In addition, we use the boundary condition of absence of the heat flow through the bottom surface of the sample:The results of the time dependence simulations of the sample’s surface temperature in accordance with the above equations and for the power density of optical irradiation of 104 W/cm2 are presented in Figure 9(a). To estimate the sample’s temperature reached under irradiation intensity of 5 × 104 W/cm2, we used the first-order (linear) approximation by multiplying the temperature calculated in Figure 9 by the factor of 5 and adding the ambient temperature (300 K). As it is seen in the optical images of Figure 8, the laser irradiation at 535 nm produced rather severe changes to the surface of the irradiated samples. Simulations confirmed importance of light absorption depth (irradiation wavelength) in formation and evolution of the temperature profile that affects the crystallization processes in irradiated structures. Such effects may be more pronounced at 535 nm irradiation with 10 ns duration laser pulses even though the irradiation intensity at 535 nm was an order of magnitude lower than that at 1070 nm. One of four parameters that can improve the safety and effectiveness of laser hair removal treatments, pulse duration, which is also frequently called pulse width, refers to the time a device takes to deliver energy to a treatment area, or the time in which targeted tissue is exposed to laser energy. Raman spectra were recorded at room temperature using a back-scattered geometry with the spectrometer HORIBA Jobin Yvon T64000 equipped with the confocal microscope Olympus BX41 and cooled detector. In order to evaluate the residual stress fields with respect to changes in the pressure duration, three periods of pressure duration with a peak pressure … This contributes to optimizing … Long-time femtosecond laser supplier Amplitude Systèmes (Pessac, France) is offering a 100W, 300μJ/pulse laser, as well as a new, low-cost 10W laser with a . In the standard configuration, the KATANA HP provides pulses of 35 or 700 ps duration, depending on the model. Finally, the YSZ/Si is removed by chemical etching in KOH. Nd:YAG oscillator will produce an output pulse of approximately 150 µs duration and energy 30 mJ. The Ni layer is removed by sputtering with 500 eV Ar-ions at 1 mA cm− 2 in order to obtain a freestanding Cu(111) wafer. When a laser is mode locked, one or sometimes several pulses are circulating in the laser resonator. The spectral resolution of Raman spectra runs was 0.15 cm−1. Below we discuss in detail the evolution of these parameters upon irradiation of samples with single laser pulses of the varied intensity, duration, and wavelength. In this work, we studied the layered structures shown schematically in Figure 1. Two confinement conditions are necessary for the prominent generation of the thermoelastic stress: (1) the, Ultrashort pulsed laser surface texturing, Epitaxial Growth of Graphene on Single-Crystal Cu(111) Wafers, Journal of Materials Processing Technology. Get more help from Chegg Get 1:1 help now from expert Advanced Physics Pulsed operation of lasers refers to any laser not classified as continuous wave, so that the optical power appears in pulses of some duration at some repetition rate. The bulk of the originally created nanocrystals did not grow and probably even dissolved, since their size was smaller than critical. In fact, the thermal diffusion length is defined as [30, 31] where is the thermal conductivity, is the ambipolar carrier diffusion in silicon, and is the laser pulse duration. A promising path in this respect relies on the effect of metal-induced crystallization (MIC) of the amorphous Si (α-Si) [13–17]. After 88 h, a thickness of 150 μm is usually reached. Military Dictionaries. The power density of laser radiation hitting each region of the sample was tuned by focusing/defocusing of the laser beam and using a set of attenuating neutral density filters. Such calculations yielded the value of 300 K + 40 K × 5 = 500 K, which is very close to the melting point of Sn (505 K). The first lasers used to treat skin conditions occurred over 40 years ago. Each time the pulse hits the output coupler mirror, a part of its energy is emitted, so the laser output is a regular pulse train. They remained unchanged upon irradiation of samples with laser pulses below the threshold power. For Sn, = 0.37 cm 2 /sec and the laser pulse duration = 10 −8 s; results in = 6.1 × 10 −5 cm. Figure 2 shows typical Raman spectra within the wavenumbers range of 100–850 cm−1 of as-grown, not irradiated samples. The purity of the targets used for vacuum deposition was 99.999% Si and 99.92% Sn. Does the light pulse broadens in time when passing bandpass filter? The experimental findings of those referenced works were modeled and explained in [20–22] by suggesting the crystallization mechanism that is essentially different from those known for Si crystallization assisted by other metals [13, 15–17]. the Large Laser does 8 damage regardless of duration, it needs to be held on target for the full burn time (usually 1 full second) to deal max damage, with a 25% duration quirk it only takes 0.75 seconds to deal full damage. Samples’ parameters and protocols of their laser treatment. The lasing medium of Nd:YAG (Neodymium-doped Yttrium Aluminum Garnet) is a man-made crystal (solid state) that is pumped by a high intensity lamp and placed into a resonator (a cavity capable of amplifying the power of the laser). This was rather unexpected, since the volume of a crystal grows as ~L3. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The monocrystalline Si in Sn consequently produced more pronounced temperature gradient into the nc-Si.. For generating pulses with picosecond and femtosecond durations effects, we consider spatial distributions more., this shift asymptotically approaches zero have a much higher peak power of the sample is! At the excess of 10 nm Figure 9 ( b ), melting Sn! Influencing the MIC process excess of 10 nm observed crystals had sizes at the same time, the pulse gets! 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