Electro-Optical Component

Abstract

An electro-optical component comprising an erbium and oxygen implanted silicon waveguide and a superconducting microwave resonator. A blocking layer of opaque material arranged between the waveguide and microwave resonator. The microwave resonator coherently coupled to spin states of the erbium.

Claims

1. An electro-optical component, the electro-optical component comprising an erbium and oxygen implanted silicon waveguide and a superconducting microwave resonator wherein a blocking layer of opaque material is arranged between the waveguide and microwave resonator and wherein the microwave resonator is coherently coupled to spin states of the erbium.

2. An electro-optical component according to claim 1 wherein the opaque material is optically opaque to 1550 nm light.

3. An electro-optical component according to claim 1 wherein the optically opaque material is a narrow bandgap semiconductor.

4. An electro-optical component according to claim 1 wherein the optically opaque material is InSb.

5. An electro-optical component according to claim 1 wherein the blocking layer comprises two layers of different materials.

6. An electro-optical component according to claim 5 where in the first layer comprises a reflective metal.

7. An electro-optical component according to claim 5 where in the first layer comprises gold.

8. An electro-optical component according to claim 5 wherein the second layer comprises an electrical insulator.

9. An electro-optical component according to claim 5 where in the second layer comprises Al.sub.2O.sub.3.

10. An electro-optical component according to claim 1 any wherein the blocking layer has a thickness of between 5 nm and 500 nm.

11. (canceled)

12. An electro-optical component according to claim 1 wherein the silicon waveguide is arranged on a silicon dioxide layer.

13. A quantum communication apparatus comprising the electro-optical component of claim 1 and further comprising a superconducting quantum computer and a photonic quantum computer; wherein the superconducting quantum computer is operably coupled to the microwave resonator and qubits of the photonic quantum computer are comprised of photons in the waveguide.

14. A method of producing an electro-optical component, the method comprising: providing a silicon substrate; implanting the silicon substrate with erbium and oxygen; annealing the silicon substrate; defining at least one optical waveguide on the silicon substrate; depositing a blocking layer of opaque material over the waveguide; fabricating a superconducting resonator structure on the semiconductor.

15. (canceled)

16. (canceled)

17. (canceled)

18. (canceled)

19. (canceled)

20. A method of producing an electro-optical component according to claim 14, wherein the erbium is implanted before the oxygen.

21. A method of producing an electro-optical component according to claim 14 wherein the erbium is implanted at energies of between 20 keV and 4000 keV.

22. A method of producing an electro-optical component according to claim 14 wherein the erbium has an average concentration of between 110.sup.14 cm.sup.3 and 110.sup.19 cm.sup.3.

23. A method of producing an electro-optical component according to claim 14 wherein the oxygen is implanted at energies of between 5 keV and 300 keV.

24. A method of producing an electro-optical component according to claim 14 wherein the annealing step comprising heating the silicon substrate to a first temperature for a first period of time and then a second temperature for a second period of time and then a third temperature for a third period of time; wherein the second temperature is higher than the first temperature and the third temperature is higher than the second temperature.

25. (canceled)

26. (canceled)

27. (canceled)

28. (canceled)

29. A method of producing an electro-optical component according to claim 14 wherein the optically opaque layer is deposited in two steps; the first with a thickness approximately equal to the height of the waveguide and the second with a thickness of between 5 nm and 500 nm; wherein the first deposition is subject to chemical-mechanical planarization prior to deposition of the second layer.

30. A method of producing an electro-optical component according to claim 14 wherein the resonator is comprised of niobium nitride.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0025] In order that the invention may be more clearly understood one or more embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, of which:

[0026] FIG. 1 is a schematic cross section of an embodiment of an electro-optical component in accordance with the invention;

[0027] FIG. 2 is a plan view of the waveguide of the electro-optical component of FIG. 1;

[0028] FIG. 3 is a plan view of the resonator of the electro-optical component of FIG. 1;

[0029] FIGS. 4a-f are schematic cross sections of an embodiment of the method of producing an electro-optical component in accordance with the invention.

[0030] FIG. 5 is a schematic cross section of an embodiment of an electro-optical component in accordance with the invention;

[0031] FIGS. 6a-d are schematic cross sections of an embodiment of the method of producing an electro-optical component in accordance with the invention.

[0032] The one or more embodiments are described above by way of example only. Many variations are possible without departing from the scope of protection afforded by the appended claims.

[0033] FIG. 1 shows a schematic cross section of an electro-optical component 10 according to the present invention. The electro-optical component comprises a silicon layer 11, on top of which is arranged a layer of silicon oxide 12 to provide a refractive index contrast layer. Arranged on top of the silicon oxide layer 12 is a first layer of InSb 13. Embedded in the first layer of InSb 13 and also arranged on top of the silicon dioxide layer 12 is an erbium and oxygen implanted silicon waveguide 14. In some embodiments the waveguide 14 and InSb 13 may be arranged directly on the silicon layer 11. The waveguide 14 and first layer of InSb 13 are covered by a second InSb layer 15 the second InSb layer 15 provides a blocking layer. Arranged on top of the second InSb layer 15 is a niobium nitride superconducting resonator 16.

[0034] By providing a layer of InSb 15 between the waveguide 14 and superconducting resonator 16, photons which escape the waveguide 14 are blocked from hitting the superconducting resonator 16. As will be appreciated by those skilled in the art, other materials, such as other narrow bandgap semiconductors, can be used to provide the blocking layer between the waveguide 14 and superconducting resonator 16, so long as they are optically opaque to light with a wavelength in the region of 1550 nm as used in the waveguide 14.

[0035] With reference to FIGS. 1 and 2, the structure of the waveguide 14 is expanded upon. The waveguide 14 is formed from a layer of silicon which has been implanted with erbium and oxygen to form erbium oxygen centres. The waveguide 14 has a rectangular cross section with a height of 300 nm and a width of 500 nm. FIG. 2 shows the path the waveguide 14 traces over the silicon oxide layer 12 as viewed from above. The path comprises nine parallel linear portions 20 each with a length of 300 m with a separation of 10 m between each portion. Adjacent portions 20 are connected by 180 degree turns 21 with bend radii of 5 m, the turns 21 are on alternating ends of the linear portions such that the individual parts form a single meandering path.

[0036] With reference to FIGS. 1 and 3, the structure of the superconducting resonator 16 is expanded upon. The superconducting resonator 16 is comprised of niobium nitride and has a rectangular cross section with a height of 100 nm and a width of 1000 nm. FIG. 3 shows the footprint of the resonator 16 on the second InSb layer 15 as viewed from above. The resonator comprises a lumped capacitor portion 31 and a coupling portion 32.

[0037] In this this embodiment niobium nitride (NbN) is used as the superconductor, but other materials could be used such as Al and Nb. The cross section of individual channels of the superconducting resonator have a height of 100 nm and a width of 1000 nm. In this embodiment the coupling portion 32 of the superconducting resonator comprises ten parallel tracks 33 approximately 250 m long and separated by a distance of approximately 30 m. Adjacent tracks are connected at alternating ends by straight connecting portions 34 arranged at 90 degrees to the parallel tracks 33. The outer most tracks 33a,b have a greater linear extent, extending beyond the coupling portion 32 by approximately 50 m. Projecting from each of these extensions 35 are five additional tracks 36. The additional tracks 36 are arranged at 90 degrees to the extensions 35 and are directed towards the opposite extension. The additional tracks 36 are neighboured by the tracks extending from the opposite extension such that they alternate and form the lump capacitor 31.

[0038] Those skilled in the art will appreciate that the exact geometry of superconducting resonator can be varied to meet the needs of coupling to the superconducting quantum computer. For example, the lumped capacitor portion 31 can be modified to achieve the resonance frequency. The superconducting resonator and the meandering waveguide structure should have approximately the same dimensions, and the superconducting resonator should be directly on top of the meandering waveguide structure such that the erbium spins in the waveguide are inductively coupled to the superconducting resonator.

[0039] With reference to FIGS. 4a-f a method of producing an electro-optical component according to the present invention is described. As shown in FIG. 4a there is provided a silicon-on-insulator (SOI) substrate 40, the substrate 40 comprises a lower silicon layer 11 and an upper silicon layer 41 with a layer of silicon oxide 12 arranged between. The substrate 40 is cooled to 77 k and then using ion implantation erbium is implanted into the upper silicon layer 41 with energies of between 50 keV and 1300 keV, until an average concentration of 110.sup.17 cm.sup.3 of erbium is achieved. The upper silicon layer 41 is then implanted with oxygen at a range of energies between 10 keV and 150 keV to an average concentration of 110.sup.19 cm.sup.3.

[0040] The implanted SOI is then annealed at 450 C. for 30 min, then at 620 C. for 180 min, then at 850 C. for 30 s.

[0041] Referring next to FIGS. 2 and 4b, using known photolithography and etching processes the upper silicon layer 41 is processed to form the waveguide 14. The portions of the upper silicon layer 41 which are not to form part of the waveguide are etched away completely to the oxide layer 12. The waveguide 14 traces a winding path as shown in FIG. 2 having the dimensions noted above.

[0042] As shown in FIG. 4c and d, a first layer of InSb 13 is then deposited to a thickness of 500 nm. As can be seen in FIG. 4 in the regions without the waveguide 14 this layer 13 extends beyond the height of the waveguide 14. Directly above the waveguide 14 the surface of the first InSb layer 13 is distorted and topographical features 42 are present. Such features 42 would affect any subsequent layers, for example the superconducting resonator 16, therefore a chemical-mechanical planarization process is undertaken on the device and the top portion of the first InSb layer 13 is removed until the surface 43 is approximately level with the upper surface 14a of the waveguide 14.

[0043] Following planarization, a second layer of InSb 15 is then deposited with a thickness of 30 nm as shown in FIG. 4e. On top of the second layer of InSb 15 a superconducting resonator 16 is deposited using known photographic techniques as shown in FIGS. 3 and 4f, as noted above the geometry of this layer can be tailored to the specific needs of the device.

[0044] The device may undergo further processing steps to allow it to be integrated into a quantum system and/or to provide protection to the component.

[0045] In use, the device is arranged in a cryostat and cooled to a temperature that results in a low probability of thermal excitation to the first excited state of the superconducting resonator, which is typically 10 to 200 mK; a magnetic field of between 0.01 and 0.5 T is also required. The waveguide 14 is operably coupled to a source of 1550 nm light which transfers a coherent optical signal from an external photonic quantum computer (not shown). The light is absorbed by the erbium centres in the waveguide 14, and changes their spin state; the spin state of the erbium centres is coupled through the InSb layer 15 to the superconducting resonator 16, thereby allowing the coherent transfer of quantum states from optical to microwave wavelengths thereby allowing the interface a photonic quantum computer and a superconducting quantum computer.

[0046] With reference to FIGS. 5 and 6 a further electro-optical component 110 according to the present invention is described. The structure of the electro-optical component 110 broadly follows that of the electro-optical 10 with corresponding features having the same numbering, advanced by 100.

[0047] FIG. 5 shows a schematic cross section of an electro-optical component 110 according to the present invention. The electro-optical component 110 comprises a silicon layer 111, on top of which is arranged a layer of silicon oxide 112 to provide an insulating layer. Arranged on top of the silicon oxide layer 112 is an erbium and oxygen implanted silicon waveguide 114. The present embodiment differs from the previous embodiment in the composition of the blocking layer. Arranged on top of the waveguide 114 and the silicon oxide layer 112 is a layer of gold 130. In some embodiments the waveguide 114 and gold may be arranged directly on the silicon layer 111. The waveguide 114 and gold layer 130 are covered by a layer of A1.sub.2O.sub.3 131 the combined gold 130 and Al.sub.2O.sub.3 131 layers provide a blocking layer. Arranged on top of the Al.sub.2O.sub.3 layer 131 is a niobium nitride superconducting resonator 116.

[0048] By providing a blocking layer of gold 130 and Al.sub.2O.sub.3 131 between the waveguide 114 and superconducting resonator 116, photons which escape the waveguide 114 are blocked from hitting the superconducting resonator 116. The use of a combination of two materials is advantageous as it allows their properties to the tailored to the two functions of the blocking layer, namely to be optically opaque to light with a wavelength of 1550 nm and to be electrically insulating. The gold layer 130 blocks the light more effectively than a narrow band-gap semiconductor and the Al.sub.2O.sub.3 layer 131 provides superior electrical insulation. As will be appreciated by those skilled in the art, other materials, for example other metals which reflect 1550 nm could be used to replace the gold layer 130 and other insulators could be used in place of the Al.sub.2O.sub.3 layer 131.

[0049] The geometry of the waveguide 114 and superconducting resonator 116 are the same as that of the earlier embodiment. Again, those skilled in the art will appreciate that the exact geometry of superconducting resonator can be varied to meet the needs of coupling to the superconducting quantum computer. For example, the lumped capacitor portion 31 can be modified to achieve the desired resonance frequency. The superconducting resonator and the meandering waveguide structure should have approximately the same dimensions, and the superconducting resonator should be directly on top of the meandering waveguide structure such that the erbium spins in the waveguide are inductively coupled to the superconducting resonator.

[0050] With reference to FIGS. 6a-d a method of producing an electro-optical component 110 according to the present invention is described.

[0051] The steps up until and including the etching of the waveguide 114 are the same as those described above. In FIG. 6a the is shown the deposition of a layer of gold 130 in place of the first InSb layer 13. Sufficient gold is deposited so as to ensure that photons which escape the waveguide 114 cannot reach the superconducting resonator 116.

[0052] On top of the gold layer 130 a layer of Al.sub.2O.sub.3 131 is deposited as shown in FIG. 6b and c. Directly above the waveguide 114 the surface of the Al.sub.2O.sub.3 layer 131 is distorted and topographical features 142 are present. Such features 142 would affect any subsequent layers, for example the superconducting resonator 116, therefore a chemical-mechanical planarization process is undertaken on the device and the top portion of the Al.sub.2O.sub.3 layer 131a is removed until the surface 143 is approximately level with the upper surface 130a of the gold layer 130.

[0053] Following planarization, a second layer of Al.sub.2O.sub.3 131 is then deposited as shown in FIG. 6d. On top of the Al.sub.2O.sub.3 layer 131 a superconducting resonator 116 is deposited as described above

[0054] The device may undergo further processing steps to allow it to be integrated into a quantum system and/or to provide protection to the component.

[0055] The one or more embodiments are described above by way of example only. Many variations are possible without departing from the scope of protection afforded by the appended claims.