Laser processing is a technique based on the interaction between a laser and the substance for cutting, drilling, cleaning, welding, and other operations on metallic or non-metallic materials. It is widely used in some important fields of the national economy such as automobiles, microelectronics, electrical appliances, aviation, metallurgy, medical treatment, and machinery manufacturing. In the process of high-powered laser processing, a large amount of plasma will be generated and there will be the obvious inverse Bremsstrahlung absorption (IBA) near the plasma plume. The effect of laser processing will be significantly deteriorated due to the absorption of laser photons and changes in light intensity distribution. Besides, laser-induced plasma is produced during the interaction between a high-powered laser and materials. Also, it has the very important value in the research of analyzing the high-powered laser processing. To fully understand the laserinduced plasma, this paper uses the Hilbert procedure to numerically investigate the plasma generated in the laser processing. The method firstly acquires the images corresponding to the fringes of a Mach–Zehnder interferometer by using the detection after a probe laser beam passing through the plasma plume. Then, a series of operations such as the spectrum shift, unwrap, and Abel inverse transformation are performed after a fast Fourier transform (FFT). Finally, the density distribution of plasma can be calculated. This methodology provides a new algorithm for the research of laserinduced plasma, and it also valuable for the understanding the high-powered laser processing process.
Because of the low thermal conductivity of the mixture gases in an alkali vapor cell, the temperature of the pumping area of an alkali vapor cell can be extremely high than that of other area. Therefore, thermally-induced effects, such as, consumption of atomic alkali, degradation of output power, glass window contamination by the products of the optically chemical reaction between atomic alkali and buffer gases, etc. can be observed in high temperature heated diode pumped alkali lasers (DPALs) in the case of high power pumping. Generally, a flowing diode pumped alkali laser (FDPAL) system is thought to be a useful way to mitigate thermal effects in a DPAL system. In the paper, a mathematical model of a flowing diode pumped cesium laser (FDPCL) was constructed to systematically study the temperature distribution, the flow filed distribution, and the impacts of pressure of the buffer gases on output power of a FDPCL, etc. The laser kinetics, heat transfer, and computational fluid dynamics (CFD) are both taken into account at the same time during the simulation. The multi-physics coupling method was utilized to solve such three physics induced problem during the simulation. It has been demonstrated that the temperature distribution of a FDPCL system depends on the distribution of gas flow filed, a gas flow method can decrease thermal effects in a DPAL system, and the output power of a DPAL can be improved by increasing the velocity of gas flow filed.
KEYWORDS: Nd:YAG lasers, Absorption, Refractive index, Rod lasers, Solid state lasers, Ray tracing, Finite element methods, Laser beam diagnostics, Reflectors
LD-side-pumping schemes for a solid-state laser offer the advantages of both high pump efficiency and high output power. However, thermally-induced lens has been known to severely affect the performance of high-powered solid-state lasers. To solve the problem, a systematic simulation model was developed by combining two procedures of ray tracing and finite element method (FEM) together to explore the thermal lens characteristics of a high-powered Nd:YAG laser. The relationship between the spatial heat density distribution and thermally-induced refractive index distribution was investigated by taking an inhomogeneous pentagonal pumping into account. The influence of a pentagonal pumping on the characteristics of the thermal lens focal length of a laser rod was studied afterwards. According to the results, if the volume average heat density of a laser rod is kept as a constant, the focal lengths of a thermally-induced lens in the pentagonal pumped laser rods will be shorter than those of the homogeneously pumped laser rods with different rod diameters. It has also been demonstrated that the focal lengths of both pumping cases are not sensitive to the variation of the rod diameter. The study is thought to be helpful for the design of a high-powered solid-state laser.
In order to satisfy the requirements of laser irradiation and laser ranging over the long distance, and to realize the miniaturization, the modularization and the engineering application of 1J high-energy DPSSL circuit system, a laser driving circuit system is designed according to the laser work patterns of one oscillator stage and two amplification stages. The system includes many parts, such as the integrated power supply circuits, the corresponding LD drivers of three stages, the signal control circuits, the Q switched circuits, the receiving circuits and the temperature control circuits, etc. It possesses the characteristics of 28VDC input power source, working frequency 25Hz,driving laser output 1J, working stable and reliable, thermal management optimization and small size as well as light weight. The study promotes the comprehensive technical specifications of the platform load effectively and can also provide a valuable reference for the miniaturization of high energy DPSSL circuit system.
A 1J LD pumped Nd;YAG pulsed laser was designed. The laser uses an oscillation and two-staged amplification structure, and applies diode bar integrated array as side-pump. The TEC temperature control device combing liquid cooling system is organized to control the temperature of the laser system. This study also analyzed the theoretical threshold of working material, the effect of thermal lens and the basic principle of laser amplification. The results showed that the laser system can achieve 1J, 25Hz pulse laser output, and the laser pulse can be output at two width: 6-7ns and 10ns, respectively, and the original beam angle is 1.2mrad. The laser system is characterized by small size, light weight, as well as good stability, which make it being applied in varied fields such as photovoltaic radar platform and etc
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