Gain measurements at 2.8μm and fluorescence spectroscopy in Er:LaF(3) waveguides fabricated by molecular beam epitaxy

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Description/Abstract

The potential of MBE rare-earth-doped LaF(3) thin films in the IR region has been previously reported by our group. Despite an unfavourable electron-phonon coupling which does not permit access to efficient transitions far above 3μm, LaF3 still offers the advantage of a very low phonon energy (~380 cm−1) and high transparency in the 2μm - 3μm range. Therefore it appears very attractive to fabricate a 2.8μm laser device based on this technology, with erbium as the doping ion, as the waveguide geometry should lead to a low-threshold, efficient, integrated device that operates continuously at room-temperature.

Several erbium-doped LaF(3) thin films were grown on (111) oriented CaF2 substrates with core depths in the 2μm range, both with or without CaF2 claddings. The design with a cladding gives a high NA of 0.7 and offers single mode properties and good vertical confinement at 2.8μm as shown in figure 1. Three samples of 19 mm length, with respective concentrations of 1.08, 5.1 and 8.9 at. %, were grown by this method for investigation.