In a collaboration with Professor Ajoy Kar and Dr Robert Thomson we have created active waveguides using femtosecond inscription in materials including Er:glass and periodically-poled KTP (a nonlinear frequency conversion crystal).
The figure opposite shows green up-conversion fluorescence emitted from an Er:glass femtosecond inscribed waveguide pumped at 980nm. Inscription in active laser glasses such as Er:glass is a promising technique for creating miniature solid-state lasers and amplifiers.
As well as laser glasses we have also achieved frequency doubling in femtosecond-laser inscribed single-mode waveguides written in two periodically-poled potassium titanyl phosphate crystals. A conversion efficiency of 0.22 %W
-1 was obtained for first-order quasi-phase matching at 980 nm and an efficiency of 0.02 %W
-1 for third-order quasi-phase matching at 800 nm. The figure opposite shows (a) an optical micrograph of the end facet of a typical waveguide written with pulse energies of 1.4 μJ, a writing speed of 50 μm s
-1 and 6 scans separated by 0.8 μm; (b) the resulting fundamental (single) mode from the guide which was polarised in the Y direction. Scales in mm. The inscribing femtosecond beam was incident upon the crystal from the top of these images.
