Model for the expansion dynamics of the laser-induced plasma and fabrication of erbium-doped planar waveguides by pulsed laser deposition and laser micromachining for up-conversion applications

Abstract

The dynamics of the laser induced plasma during pulsed laser deposition of BaTiO₃ thin films is studied theoretically and experimentally and related to the resulting film properties. The expansion of the laser induced plasma is modelled taking inelastic collisions between ablated particles and processing gas particles into account. The predictions of the model are in agreement with data from high speed photography of the plasma emission. Pulsed laser deposition with KrF excimer laser radiation (wavelength 248nm, pulse duration 20 ns) is used to grow dense, transparent, amorphous, poly-crystalline and single crystalline erbium doped BaTiO3 thin films for photonic applications. Visible emission due to up-conversion luminescence (wavelength 528 nm and 548 nm) under excitation with diode laser radiation at a wavelength of 970-985 nm is investigated as a function of the erbium concentration of 1-46 mol % and structural film properties. The dielectric films are micro machined to form optical wave guiding structures using Ti:sapphire laser radiation (wavelength 810 nm, pulse duration 63-150 fs) by scanning the focussed laser beam relatively to the sample.