Single quantum emitters can be used as light sources that launch single photons on-demand into on-chip waveguides, constituting an important resource for integrated quantum photonic applications. While illumination with laser light resonant with a quantum emitter embedded in a waveguide is necessary for production of highly indistinguishable, waveguide-bound single-photons, leakage of the excitation laser into the waveguide must be strongly suppressed. Illumination with a free-space laser beam perpendicular to the waveguide is currently used for such purpose, with limited efficacy and controllability. These issues are solved through illumination of the emitter via a higher order confined mode of the hosting waveguide, introduced by a secondary on-chip waveguide evanescently coupled to the former, and extraction of the single-photon stream though a third waveguide in similar fashion.
The invention is an integrated photonic device which allows production of a pure stream of on-chip waveguide-bound indistinguishable single-photons from the resonance fluorescence of a single quantum emitter embedded in a multimode on-chip waveguide, for which the quantum emitter is excited by on-chip waveguide-bound resonant laser light.
There are currently no commercial products that involve on-demand production of single-photons in on-chip waveguides. In the laboratory, however, resonant optical excitation of single quantum emitters in waveguides, for on-demand generation of indistinguishable waveguided single-photons, is typically done through a free-space optical beam perpendicular to the chip surface, from an off-chip laser source. Furthermore, the emitted single-photons are emitted into the same waveguide in which the quantum emitter is embedded.
While in the new scheme some undesirable amount of the excitation laser power may still leak into the single-photon output waveguide, the level of purity of the single-photon stream may be more carefully optimized, as compared to the free-space excitation mode, by controlling the degree of coupling between modes in the SM and MM waveguides, and the emitter-waveguide coupling -factors, which can be done by simple modifications to the on-chip waveguides’ dimensions.
A further advantage of this scheme is that it can be more simply integrated with on-chip, waveguide-coupled lasers that may act as the excitation source to the quantum emitter.