Population mechanisms of the green Er3+:LiYF4 laser

In computer simulations the mechanisms that lead to room-temperature continuous-wave green upconversion lasing in Er3+:LiYF4 are investigated. The rate-equation system considers the full erbium level scheme up to 2H9/2, ground-state depletion, excited-state absorption on the pump and laser wavelengths, three interionic processes, stimulated emission, and the crystal and resonator data of the experiments. Experimental results performed at the University of Hamburg, Germany, are reproduced in the simulation. The influence of different parameters as pump wavelength, absorption cross sections, interionic parameters, dopant concentration, and temperature is investigated. An avalanche effect which exploits the strong cross relaxation from the upper laser level and the upconversion from 4I13/2 leads to an efficient population of the upper laser level. At higher dopant concentrations the cross relaxation becomes detrimental to stimulated emission due to the depletion of the upper laser level. This concentration dependence can be considered as a general behavior of rare-earth-doped avalanche lasers

Excited-state absorption in ZBLAN:Er3+: implications for a diode-pumped 3-µm fiber laser

Effective excited-state absorption (ESA) cross-sections are measured in ZBLAN:Er3+ at 780-840 nm. Pump losses by ESA are present over the whole absorption band. Diode pumping at 979 nm seems more favorable for high-power 3-µm fiber lasers

Model and computer simulation of nanosecond laser material ablation

A computer model to simulate the evolution of parameters describing laser ablation processes was developed. The absorbed laser energy, the heat diffusion, the phase transformations and the shielding effect of the ablated material were taken into account. The temporal development of the ablated volume, pore depth and extension of the melt zone were calculated for single pulses of 500, 100, 20, 5 and 1ns. Simulations were performed for pulse energies of 50μJ and spot diameters of 10μm. From temporal evolution curves of the ablated volumes, the stoppage of the ablation process was evidenced before the end of the processing pulse. Comments with respect to optimal pulse duration (in the ns regime) are also formulate

Selective laser sintering of amorphous metal powder

For the first time, selective sintering of amorphous PtCuNiP powder with a pulsed Nd:YAG laser has been studied. Upon pulsed interaction, the grains melt only superficially to build necks between the grains. Depending on the laser parameters, the sintered material can be crystallized or retained amorphous. By contrast with crystalline powder, laser sintering of amorphous powder is achieved at substantially lower pulse energies due to its low melting point. The obtained results are compared with previous results from selective laser sintering of titanium powde

Investigation of diode-pumped 2.8-µm laser performance in Er:BaY2F8

Laser operation at 2.8 mm in BaY2F8 with erbium concentrations of 7.5% and 20% is investigated under laser-diode pumping at 967 nm. Output powers as high as 250 mW and slope efficiencies as high as 24% are obtained. Results are comparable with those of Er3+:LiYF4 under the same pump conditions. Slope efficiencies above 30% are predicted for optimized erbium concentrations