Decrease In Laser Output Power Research Articles

Microstructure – Properties relationship in laser-welded AZ31B magnesium alloy

The AZ31B magnesium alloy was laser-welded at three different (1.2, 1.6, and 2 kW) laser output powers in the present work. All the butt weld joints are almost defect-free. The size of the weld joint slightly increases with increasing laser output power. The weld metal is formed by columnar grains of the alpha phase at the weld metal/base metal interface, but a finely equiaxed grain microstructure is formed in the centres of fusion zones. The minor phases are Mg17Al12 and (Al,Mg)8Mn5. The weld metal microstructure manifests clear refinement with a decrease in laser output power. Microstructural changes are reflected in changes in mechanical properties; weld joints prepared at the lowest laser output power manifest the highest microhardness, ultimate tensile strength, yield strength, and almost 90% joint efficiency. This is related to the different extents of strengthening mechanisms that act most effectively in weld joints made at 1.2 kW laser output power. Detail analysis of fracture surfaces confirmed that lower laser output power and general microstructural refinement favours the formation of plastically deformed material, which is in excellent agreement with both the experimentally determined and the calculated values of yield strength.

Gas contaminant effects in discharge-excited KrF lasers

Infrared, ultraviolet, and mass spectrometers are used to study the evolution of gaseous impurities as a function of time in a discharge-excited KrF laser. The major contaminants detected, listed in order of prominence, are HF, CF(4), COF(2), SiF(4), and CO(2). The effect of each of these individual impurities on the laser performance is measured, and the results are used in a simple model that accurately predicts the decrease in laser output power with time. Techniques for improving the gas lifetime in KrF lasers are alsodiscussed.

Discharge pumped C1F laser at 285 nm

This paper reports on experiments carried out in order to improve the performance of the TEA discharge pumped C1F uv laser at 285 nm. Factors which influence the gas degradation with increasing operating time, resulting in a decrease of laser output power, were investigated, aiming at a better understanding of the relevant mechanisms. By optimizing several parameters, laser pulse energies beyond 25 mJ were obtained in a high-pressure discharge laser chamber. C1F lasing has also been demonstrated in a commercially available multigas TEA laser system.

Thermal behavior of NdP5O14 lasers

Thermally induced changes in the output behavior of a quasi-cw NdP5O14 laser under different pump duty cycles have been studied both theoretically and experimentally. With a cavity design which supports thermally stable Gaussian modes, no anomalous mode or spectral changes were observed under different heating or drive conditions. The magnitude of the remaining thermal effects on the microscopic lasing properties of the material are reviewed and compared. The decrease of laser output power at high average excitation levels is attributed mainly to a terminal state population increase with rising temperature, and results calculated from this model are in good agreement with the experimental data.

Analysis of Kiton Red S dye degradation effects on the output energy of the pulsed organic dye laser

Dyes that lase in the long wavelength range about 550 nm into the IR region are characterized by long conjugated chains that are particularly susceptible to photodecomposition. A model was developed, based on a four-level laser system, to provide a means of assessing the relative importance of various factors which contribute to a decrease in laser output power. The model, based on a steady state analysis of the laser rate equations, was applied to the case of Kiton Red S laser beam energy degradation. Parameters were estimated on the basis of experimental or reported values for Kiton Red S or for other similar xanthene dyes. It was discovered that, while a decrease in dye concentration and absorption of pump radiation by the decomposition product can make small contributions to laser beam energy decay, the most critical effect is the absorption of laser photons by the decomposition product of the dye.