A fluorescent structure comprising a plurality of quantum dots that radiate emission in response to optical pumping. These quantum dots are disposed in relation to a waveguide so as to be able to propagate this emission through the waveguide. Preferably, the fluorescent structure comprises a layer of quantum dots sandwiched between two layers, at least one layer being optically transmissive to the pump radiate and at least one of the layers being optically transmissive to emission from the quantum dots.