Photonic circuitry having multiple optical resonators

1 . An optical device, comprising:

a first ring resonator with a first radius;

a second ring resonator with a second radius;

a third ring resonator with a third radius and stacked directly under the first ring resonator;

a fourth ring resonator with a fourth radius and stacked directly under the second ring resonator; and

an optical waveguide feeding the first and second ring resonators in parallel, wherein the first and second ring resonators are positioned on opposing sides of the optical waveguide, wherein the optical waveguide includes a straight rail, wherein when viewed from top a virtual line connecting centers of the first and second ring resonators is perpendicular to a lengthwise direction of the straight rail, and wherein the first and second ring resonators and the optical waveguide are embedded in a dielectric layer disposed above a semiconductor substrate.

2 . The optical device of claim 1 , wherein the first and second ring resonators include an optical medium providing a third-order nonlinear optical susceptibility.

3 . The optical device of claim 1 , wherein the optical waveguide is split into a first portion partially surrounding the first ring resonator and a second portion partially surrounding the second ring resonator.

4 . The optical device of claim 3 , wherein the first portion partially surrounds the first ring resonator for half a circle, and the second portion partially surrounds the second ring resonator for half a circle.

5 . The optical device of claim 3 , wherein a distance between the first portion and a circumference of the first ring resonator remains constant, and a distance between the second portion and a circumference of the second ring resonator remains constant.

6 . The optical device of claim 1 , wherein the first radius equals the second radius, and the third radius equals the fourth radius.

7 . The optical device of claim 1 , wherein the optical waveguide is split into a first branch feeding the first ring resonator and a second branch feeding the second ring resonator.

8 . The optical device of claim 1 , further comprising:

a second optical waveguide coupled with the third ring resonator; and

a third optical waveguide coupled with the fourth ring resonator.

9 . The optical device of claim 1 , wherein the optical waveguide is a first optical waveguide, the optical device further comprising:

a second optical waveguide configured to receive photons escaping from the first ring resonator, wherein a distance between the first optical waveguide and a top surface of the semiconductor substrate is different from a distance between the second optical waveguide and the top surface of the semiconductor substrate.

10 . The optical device of claim 1 , wherein the first radius equals the third radius, and the second radius equals the fourth radius.

11 . An optical device, comprising:

a first ring resonator with a first radius;

a second ring resonator with a second radius;

a first optical waveguide directly injecting photons into the first ring resonator; and

a second optical waveguide accepting photons escaping from the second ring resonator, wherein the first and second ring resonators are positioned between the first and second optical waveguides, wherein the first and second ring resonators and the first and second optical waveguides are all disposed above a top surface of a semiconductor substrate, and wherein a distance between the first ring resonator and the top surface of the semiconductor substrate is different from a distance between the second ring resonator and the top surface of the semiconductor substrate.

12 . The optical device of claim 11 , wherein the second optical waveguide is coupled to the second ring resonator through near-field coupling.

13 . The optical device of claim 12 , wherein the near-field coupling is near-field conformal coupling.

14 . The optical device of claim 12 , wherein the near-field coupling is near-field circumferential coupling.

15 . The optical device of claim 11 , wherein the first radius is larger than the second radius.

16 . The optical device of claim 11 , wherein the first optical waveguide includes a tapering portion that is in direct contact with a circumference of the first ring resonator.

17 . A method, comprising:

sending a source light beam into a first optical waveguide, wherein the first optical waveguide has a first straight rail extending lengthwise along a first direction;

direct injecting the source light beam into a first ring resonator through an end portion of the first optical waveguide that is in physical contact with the first ring resonator, wherein a fraction of the source light beam is converted into a signal light beam via a spontaneous four-wave mixing process;

coupling photons in at least the signal light beam into a second ring resonator through near-field coupling between the first ring resonator and the second ring resonator; and

coupling the photons into a second optical waveguide through near-field coupling between the second ring resonator and the second optical waveguide, wherein the second optical waveguide has a second straight rail extending lengthwise along a second direction that is different from the first direction,

wherein the first and second ring resonators and the first and second optical waveguides are all embedded in a dielectric layer disposed above a top surface of a semiconductor substrate.

18 . The method of claim 17 , wherein a portion of the second optical waveguide partially surrounds the second ring resonator.

19 . The method of claim 17 , wherein the second ring resonator suppresses auxiliary resonance within the first ring resonator.

20 . The optical device of claim 11 , wherein the first radius equals the second radius.