High numerical aperture planar waveguides

Rare earth doped planar crystal waveguides have the potential to yield efficient compact diode pumped lasers and amplifiers. Confinement of pump and signal to the waveguide core leads to high small-signal gains for amplifiers and, if additional propagation losses are small, low laser thresholds. The planar geometry is well matched to the asymmetric output of high average power diodes, simplifying the coupling and mode-matching requirements. The natural slab geometry is also ideal for thermal management. Coupling the highly divergent output of high power diode lasers into waveguides, either by focussing or proximity coupling, requires relatively thick waveguides (>10µm) and, especially for proximity coupling, a high numerical aperture (NA). We report two fabrication methods that can meet these requirements; pulsed laser deposition (PLD) and thermal bonding. The fabrication details and waveguide characterisation, including Ti:Sapphire pumped laser operation, will be discussed