Emission and excitation spectra of Er-doped YAP crystals reveal a broad emission band in the eyesafe region with peaks
around 1545-nm and 1608-nm and pump-bands suitable for common 800-nm and 970-nm diode lasers, suggesting YAP
as a candidate crystalline host for diode-pumped laser in the 1.5-μm eyesafe regime. Erbium-doped YAP-crystal results
are comparable with analogous measurements on Er:Yb:YAG, which has already demostrated efficient lasing action in
the eyesafe region.
Diode-pumping with appropriately modulated pulses is used to expose subtle input / output pulse-timing characteristics
of Er3+:Yb3+-codoped systems, particularly Er3+:Yb3+:glass and Er3+:Yb3+:YAG, and study their relation to laser
efficiency. In free-running operation, these systems may persist to lase for uncommonly long time periods (up to a ms)
after the pump stops. In Q-switched operation, maximum laser output is obtained only if Q-switching is purposely
delayed for some significant additional time (typically 50-500μs) following the end of the pump pulse. Furthermore,
pump-pulse duration affects profoundly the Er3+:Yb3+-laser output performance, especially in Q-switched mode.
Numerical modeling simulations are presented, accounting for the observed effects and extrapolating them to novel
regimes of Er3+:Yb3+-laser operation.
Q-switched operation of a novel transversely-diode-pumped bulk 1.65μm Er:Yb:YAG laser is demonstrated using a piezoelectric "FTIR" type of Q-switch. Typical output pulses of approximately 12mJ energy and 4011s duration have been obtained, suitable for telemetry and other applications. The material is transversely pumped using quasi-cw 960-nm laser-diode arrays. In Q-switched mode, lasing threshold lies in the range of 0.5-1.4J, depending on pumping conditions and output coupling, while optical slope efficiencies in the order of 1% were measured with respect to the incident pump energy. The reported system represents a rare-earth crystalline laser with superior active material and optical qualities, to challenge the established glass-host materials in the 1.6μm eyesafe wavelength region.
We describe an application of laser cleaning of metallic wheels with a Q-switched Nd:YAG laser. The beam is divided in four parts injected into fibers, sent on an automated machine for stripping the protective varnish on metal sheets, parts of large electrical motors, before soldering of cylindrical spacers via an electrical discharge.
Pulsed Er3+:Yb3+:YAG is a novel crystalline diode-pumped laser capable of delivering high pulse energies in the 1.5-
1.7μm "eye-safe" region. This work reports efficient lasing in long-pulse and in Q-switched mode, with pulse energies in
the order of 10's of mJ, employing standard 960-nm quasi-cw semiconductor laser arrays in a direct transverse diodepumping
configuration. In free-running mode, 83mJ output, 15% slope efficiency and 0.24J pump threshold have been
attained. Q-switched operation was realized with a "frustrated total internal reflection (FTIR)" device, yielding 12.5mJ
single pulses of 41-ns FWHM duration with smooth temporal and spatial profiles. Pump temperature-tuning and pulse
duration effects on laser performance were also investigated, whereas pumping parameters optimizing pulse energy and
efficiency were determined.
We demonstrate efficient lasing of bulk diode-pumped Er3+:Yb3+:YAG at 1.645 µm. The material is transversely pumped using three quasi-cw 960-nm laser diode arrays in a simple arrangement. In the free-running mode of operation, an output pulse energy of 79 mJ is obtained at 4.7 J of incident optical pump energy. The lasing threshold lies in the range 1.0 to 1.9 J in long-pulse operation, depending on pumping conditions, and optical slope efficiencies of 2.2% to 3.4% were measured with respect to the incident pump energy. Furthermore, initial Q-switching experiments with a Co:MALO saturable absorber yielded pulses of 1.7-mJ energy and 340-ns FWHM duration. As the reported laser setup also has an uncomplicated and compact design, it represents a good crystalline rare-earth candidate system with superior material qualities to compete against the established glass-host materials in the eye-safe wavelength range.
Efficient lasing at 1.645mm of bulk diode-pumped Er3+:Yb3+:YAG is demonstrated. The material is transversely pumped using three quasi-cw 960-nm laser-diode arrays in a simple arrangement. In free-running mode of operation, output pulse energy of 79mJ is obtained at 4.7J of incident optical pump energy. Lasing threshold lies in the range of 1.0-1.9J in long-pulse operation, depending on pumping conditions, while optical slope efficiencies of 2.2-3.4% were measured with respect to the incident pump energy. Furthermore, initial Q-switching experiments with a Co:MALO saturable absorber yielded pulses of 1.7mJ energy and 340ns FWHM duration. As the reported laser setup is also characterized by an uncomplicated and compact design, it represents a good crystalline rare-earth candidate system with superior material qualities to compete against the established glass-host materials in the eyesafe wavelength range.
In the present work, the effects of nanosecond pulsed laser irradiation on oxidized metallic surfaces were investigated, in order to estimate the possibility of using laser techniques for cleaning applications. After oxidation, the oxide layer developed on the metallic surfaces depends on the composition of the substrate and also on oxidation conditions. In this study a modeling system: pure Fe oxidized at 500 degrees C, has been investigated. The influence of the optical properties of the oxide films on the removal mechanisms and the cleaning efficiency of the laser technique was illustrated by performing specific electrochemical treatments.
Laser beam transmission through optical fibers is presented in comparison with other techniques for laser cleaning applications. We describe the parameters of importance for a fiber-user and emphasize on the particularities connected to the injection of very high peak power Q-switched lasers into fibers. A description of the last laboratory and commercial developments of cleaning systems with fiber transmission is given, either with single or multiple fibers.
Significant problems in deep laser spot welding are formation of welding defects, and particularly porosities in the case of tantalum joining. In this study, we investigate and model porosities forming and trapping. Two types of porosity are observed: (1) Small porosities are round shape bubbles of less than 250 micrometer diameter. These defects may come from gas bubbles generated following hydrogen rejection during solidification or they may come from bubbles induced by both an intense evaporation inside the keyhole and a turbulent flow in the molten pool. (2) Large porosities are voids generated in the bottom of the welded zone. They arise from a lack of matter inside the weld as if the molten metal have not had enough time to fill up the keyhole completely before it solidifies. We elaborated a numerical model for the comprehension of little porosities trapping by comparing the calculated spot weld solidification time to the rising time of bubbles in the liquid phase. We also studied the melt flow back into the keyhole in order to explain the formation of the observed large voids. These two models are in good agreement with experimental observations, in particular with X-ray radiographs achieved during the solidification of tantalum spot welds.
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