Patent US9148225

Optical transmitters and receivers for quantum key distribution
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US9148225

1. An optical receiver for a quantum key distribution system, the optical receiver comprising a plurality of optical components mounted or formed in a substrate and optically coupled by one or more hollow core waveguides formed in the substrate, wherein (4) (5)

at least one of said optical components is a mounted component retained in an alignment slot, wherein:

(i) the alignment slot is formed in the substrate,

(ii) a longitudinal axis of the alignment slot is a longest dimension of the alignment slot that transversely intersects a longitudinal section of one of said hollow core waveguides, and

(iii) the alignment slot defines an alignment of the optical component retained within the alignment slot with respect to said hollow core waveguide, and

the at least one of said optical components is inserted into the alignment slot.

2. The optical receiver according to claim 1, wherein: (0) (4)

(i) the alignment slot comprises a first portion and a second portion that are formed in the substrate,

(ii) the first portion and the second portion of the alignment slot share the longitudinal axis and are separated by the one of said hollow core wave guides,

(iii) the first portion and the second portion of the alignment slot retain the at least one optical component, and

(iv) the alignment of the optical component retained within the alignment slot is defined by an angle at which the alignment slot transversely intersects the one of said hollow wave guides.

3. The optical receiver according to claim 1, the optical receiver comprising first and second receiver channels, each receiver channel being arranged to detect a photon polarised in one of a respective pair of orthogonal polarisation states and to distinguish the polarisation state of that photon, respective pairs of polarisation states being mutually inclined. (2) (0)

4. The optical receiver according to claim 3, the optical receiver comprising means for randomly directing an input photon to one of the receiver channels. (2) (0)

8. The optical receiver according to claim 3, wherein the first receiver channel comprises a first polarising beam splitter and two single-photon detectors, the polarising beam splitter having two outputs each of which is optically coupled to a respective single photon detector by a respective hollow core waveguide formed in the substrate. (1) (0)

17. The optical receiver according to claim 1, wherein the substrate comprises a base portion having one or more square cross-section channels formed therein, and wherein a lid portion is additionally provided to form said one or more hollow core waveguides. (1) (0)

19. A base portion for an optical receiver according to claim 1, the base portion comprising a plurality of alignment slots and connecting hollow channels formed in a substrate, each alignment slot being adapted to receive in alignment an optical component. (0)

10. An optical transmitter for a quantum key distribution system, the optical transmitter comprising a plurality of optical components mounted or formed in a substrate and optically coupled by one or more hollow core waveguides formed in the substrate, wherein (4) (5)

at least one of said optical components is a mounted component retained in an alignment slot, wherein:

(i) the alignment slot is formed in the substrate,

(ii) a longitudinal axis of the alignment slot is a longest dimension of the alignment slot that transversely intersects a longitudinal section of one of said hollow core waveguides, and

(iii) the alignment slot defines an alignment of the optical component retained within the alignment slot with respect to said hollow core waveguide, and

the at least one of said optical components is inserted into the alignment slot.

11. The optical transmitter according to claim 10, the optical transmitter comprising an optical source and a polarisation modulator, the optical source and the polarisation modulator being mounted or formed in the substrate and optically coupled by one or more hollow core waveguides formed in the substrate. (1) (0)

15. The optical transmitter according to claim 10, further comprising an intensity modulator mounted or formed in the substrate and arranged to control the output intensity of the optical transmitter. (0)

16. The optical transmitter according claim 10, wherein the intensity modulator is a Mach-Zehnder interferometer device comprising an MMI splitter and an MMI recombiner. (0)

20. A base portion for an optical transmitter according to claim 10, the base portion comprising a plurality of alignment slots and connecting hollow channels formed in a substrate, each alignment slot being adapted to receive in alignment an optical component. (0)

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Patent US9148225

Optical transmitters and receivers for quantum key distribution

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