Abstract: This disclosure relates to an optical device comprising: a first filter waveguide section having an input for receiving a pump signal, the first filter waveguide section further having an output; an emitter waveguide section having an input coupled to the output of the first filter waveguide section to receive a transmitted pump signal therefrom, the emitter waveguide section supporting at least a first guided lower-order optical mode and a second guided higher-order optical mode, the emitter waveguide section comprising a photon emitter coupled to the first guided mode to emit radiation into the first guided mode and coupled to the second guided mode to allow optical pumping of the photon emitter by pump signal power carried in the second guided mode, the emitter waveguide section further having an output for outputting radiation emitted from the photon emitter; a second filter waveguide section having an input coupled to the output of the emitter waveguide section and having an output, the second filter wav