Rare earth doped fluoride waveguides fabricated using molecular beam epitaxy

We have grown planar waveguides of rare earth doped single crystal fluoride films on insulating and semiconductor substrates using molecular beam epitaxy and have formed channel waveguides by ion milling. Structural and spectral analysis demonstrates that excellent crystallinity is being achieved and that the rare earth ion is incorporated into the film at sites and in charge states similar to bulk laser hosts. Lifetime measurements confirm that the local environment of the dopant ion is essentially that found for bulk materials. Single and higher order optical mode propagation has been demonstrated for the channel waveguides. By exciting individual channels with an 800 nm pump, we have generated strong upconversion fluorescence in Er and Nd doped guides. The ability to fabricate these waveguides On semiconductor substrates substantiates the potential for on chip integration of both IR downconversion lasers and IR pumped upconversion visible and UV lasers with a diode laser pump source. The use of transition metal dopants is possible and would enable tunable operation. Waveguide propagation loss in present devices must be reduced to realize a laser oscillator and we discuss how this is being addressed.<
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