The graphs presented here show results of numerical simulation of the temporal evolution of the output power of a Tm3+:ZBLAN fiber. The results are presented as a phase map of the power as a function of the population inversion. This speciality fiber is of great interest because it has a low phonon energy. It is then possible to pump successively several energy levels by an upconversion process with a single IR laser source. When pumped to their 1G4 level Tm3+ ions could emit photons around 800 nm by two different way, the 1G4 3H5 transition (785 nm) and the 3H4 3H6 transition (805 nm). However, those photons can be reabsorbed by the ground level that plays the role of a saturable absorber. The laser exhibits then a self-pulsed behaviour that is well seen on the graphs: as soon as the laser starts to oscillate, pulses are emitted continuously. The map tends to a stable trajectory meaning that the laser enters in a periodic regime.
Guillaume Androz is an engineer who graduated from the National School of Physics (ENSPG) in Grenoble, France. He is currently a Ph.D student at the Center of Optics Photonics and Laser (COPL) at Laval University, Québec, Canada.