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To this end, in 1996, and others for Fused Silica Stwart the ablation threshold in-depth study found that the pulse width <10 ps range, the ablation threshold with no change in pulse width increases. Therefore, researchers have proposed avalanche generation rate of free electron laser peak intensity is proportional to the linear model, and use the following non-linear rate equation, the dielectric model of femtosecond laser threshold. And other surrounding almost no impact. The reason is that more than multi-photon absorption threshold has generated some of the absorption, and electron temperature with the surrounding lattice in the case of non-equilibrium state caused by ablation. When the pulse width> 20 ps ablation, the electrical ablation zone in the heat-affected layer, it is difficult to carry out precision machining. The green laser pointer   company can provide the OEM production of  green laser pointer      .
The laser ablation process media media ablation process, the first multi-photon absorption produce seeds with free electrons, and free electron absorption and ion collisions through the traditional, the plasma density is increased. Multi-photon absorption is dependent on the peak intensity of the nonlinear absorption process, the higher the peak intensity, the greater the rate of multi-photon absorption. For example, fused silica band gap of about 9.0 eV, so the wavelength of 800 nm (1.55 eV) light, fused silica produced six-photon absorption process, so a very short pulse ablation threshold depends on the medium to determine the on. The pulse width is wider, the light intensity decreased leading to multi-photon absorption reduction of defects caused by impact ionization of impurities are areas of probability theory. Kaut and others use 5 fs and 220 fs pulse width of femtosecond lasers for fused silica and borosilicate glass to study the shape of the ablation process, and confirmed that the pulse width of 5 fs, it can be reproducible, controlled high the ablation process. This kind of   usa green laser pointer     has the function of browsing the document.
The ablation process of metals is different from the metal media, which from the beginning have enough free electrons (conduction electrons) exist, so the metal can absorb the laser pulse energy. In the past with> 1 ns pulse width laser ablation of metals, high thermal conductivity layer of thermal effects, it is difficult to achieve precision machining. However, the femtosecond laser in the electronic and lattice to reach thermal equilibrium before the completion of injection of energy (see Figure 2). The results showed that in the melt prior to ablation, almost no heat-affected layer. Nolte, who described the use of two-temperature model of laser ablation threshold of the metal and pulse-width dependence. When the use of femtosecond laser pulses, the ablation threshold using the following equation: dn = r (I) n + P (I) dt where n is the free electron density, r is the avalanche rate, P is the multi-photon absorption rate. The superiority of green laser pointer should be stated in the front page of the booklet.
In this model, set free electron density reaches a critical plasma density (nc = 1021n - 2 cm-3, "(" m) for the laser wavelength) for the ablation threshold. Stuart, who's the model with the Keldysh theory of multi-photon absorption combined, obtained the following conclusions. That is, pulse width <100 fs femtosecond laser ablation in the media almost ignored the generation of free electron avalanche effect, and multi-photon absorption dominates. In Stuart, who designed the model, the pulse width is less than 10 ps ablation threshold within the range of changes with the pulse width decreases. During this minimum 5 fs laser ablation experiments have been resolved. Pulse width <20 ps laser ablation experiments has the advantage of the media, ablation limited to the peak incident laser beam cross-section of part of the heat-affected layer Fth ≌ # $ / # (2) where% is the material density, $ to burn loss of heat required, # for the optical absorption coefficient. The battery of    green laser pointer      has the long life span.
From (2) shows that the ablation threshold and pulse width has nothing to do, only with the material characteristics. When using nanosecond laser pulses, the threshold of 22 optical and electrical corrosion Rao information Mar. 2007 Laser Technology and Applications Laser Technology & Applications femtosecond laser ablation of femtosecond laser irradiation GaAs semiconductor substrate, the molten state can pump probe observation of changing circumstances over time. If the light pulse to 100 fs, the resulting fast and slow melting of two kinds of molten melt. High energy laser irradiation from Mobile, electronic excitation into the state, and have a "non-hot-melt, non-uniform melting." This kind of    green laser pointer      has the fashionable appearance design.