Compact optical resonator with enhancement features

A photonics structure, comprising:

• a first ring optical waveguide on a substrate;
• a first rail optical waveguide configured to couple a first light into the first ring optical waveguide;
• first enhancement features configured around the first ring optical waveguide and the first rail optical waveguide;
• a second ring optical waveguide on the substrate;
• a second rail optical waveguide configured to couple a second light into the second ring optical waveguide;
• and
• second enhancement features configured around the second ring optical waveguide and the second rail optical waveguide, wherein
• the first ring optical waveguide, the first rail optical waveguide and the first enhancement features are positioned at a first level over the substrate,
• the second ring optical waveguide, the second rail optical waveguide and the second enhancement features are positioned at a second level over the substrate, and
• the second level is different from the first level.

A photonics structure, comprising:

• a first optical ring resonator on a substrate at a first level, wherein the first optical ring resonator further includes a first ring optical waveguide, a first rail optical waveguide configured to couple a first light into the first ring optical waveguide, and first enhancement features configured around the first ring optical waveguide and the first rail optical waveguide;
• a second optical ring resonator on the substrate at a second level, wherein the second optical ring resonator further includes a second ring optical waveguide, a second rail optical waveguide configured to couple a second light into the second ring optical waveguide, and second enhancement features configured around the second ring optical waveguide and the second rail optical waveguide;
• and
• a third optical ring resonator on the substrate at a third level, wherein the third optical ring resonator further includes a third ring optical waveguide, a third rail optical waveguide configured to couple a third light into the third ring optical waveguide, and third enhancement features configured around the third ring optical waveguide and the third rail optical waveguide, wherein
• the first, second and third levels are different from each other,
• the first, second and third ring optical waveguides are vertically aligned, and
• the first, second and third enhancement features have a width less than that of the first, second, and third ring optical waveguides.