Guided light source for emission of single photons

1. A guided light source, comprising:

at least one quantum box associated with a discoid wave guide to achieve cylindrical propagation of a wave front emitted by the at least one quantum box in the discoid wave guide;

an annular wave guide surrounding said discoid wave guide, having a grating coupler formed on its internal periphery to receive said wave front in normal incidence and being open at two coupling ends;

an output wave guide optically coupled to the annular wave guide; and

a coupler having a first side connected to the two coupling ends of the annular wave guide and a second side connected to the output wave guide, said coupler being configured to combine a beam circulating in the annular wave guide in a propagation mode and a beam circulating in the annular wave guide in a counter-propagation mode into a single beam circulating in the output wave guide.

2. The guided light source according to claim 1 , in which the coupler is a Y junction.

3. The guided light source according to claim 1 , in which the coupler is a multimode interference coupler.

4. The guided light source according to claim 1 , further comprising a mirror that surrounds the annular wave guide.

5. The guided light source according to claim 4 , in which the mirror is arranged at a quarter wave optical distance from the annular wave guide.

6. The guided light source according to claim 1 , in which the discoid wave guide and the annular wave guide are separated from each other by an optical distance less than a quarter wavelength distance.

7. The guided light source according to claim 1 , in which the at least one quantum box is arranged in the discoid wave guide.

8. The guided light source according to claim 1 , in which the at least one quantum box and the discoid wave guide are separated from each other by an optical distance less than a quarter wavelength distance.

9. The guided light source according to claim 8 , in which the annular wave guide is made of doped semiconductor material.

10. The guided light source according to claim 8 , in which the annular wave guide is a rib wave guide.

11. The guided light source according to claim 9 , further comprising an electrical contact pad arranged above the at least one quantum box.

12. The guided light source according to claim 1 , in which the at least one quantum box is a single quantum box.

13. A method of emitting a sequence of single photons, comprising exciting the single quantum box of the source according to claim 12 by optical or electrical pumping.

14. A method of fabrication of a guided light source, comprising:

forming a discoid wave guide, an annular wave guide surrounding the discoid wave guide and being open at two coupling ends and an output wave guide optically coupled to the annular wave guide;

positioning at least one quantum box with respect to the discoid wave guide to achieve cylindrical propagation of a wave front emitted by the at least one quantum box in the discoid wave guide;

forming a grating coupler on an internal periphery of the annular wave guide to receive said wave front in normal incidence; and

forming a coupler having a first side connected to the two coupling ends of the annular wave guide and a second side connected to the output wave guide, said coupler being configured to combine a beam circulating in the annular wave guide in a propagation mode and a beam circulating in the annular wave guide in a counter-propagation mode into a single beam circulating in the output wave guide.