Photonic structures with one or more notched side edges

#The disclosure relates to photonic chips and, more specifically, to structures for a photonic chip that include a photonic device, such as a ring resonator, and methods of forming such structures.

#Photonic chips are used in many applications and systems including, but not limited to, data communication systems and data computation systems. A photonic chip includes a photonic integrated circuit comprised of photonic devices, such as modulators, polarizers, and optical couplers, that are used to manipulate light received from a light source, such as an optical fiber or a laser.

#A ring resonator is a photonic device that is characterized by a circular waveguide core with a resonance condition in which specific wavelengths of light circulating in the circular waveguide core are captured. Specifically, wavelengths of light that are equal to the circumference of the circular waveguide core divided by an integer and multiplied by the refractive index of the surroundings are captured and resonate within the ring. Non-resonant wavelengths of light are free to be released from the ring resonator. The resonant wavelengths of light that are captured by the ring are observed as dips in the spectrum of light released from the ring resonator.

#The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various embodiments of the invention and, together with a general description of the invention given above and the detailed description of the embodiments given below, serve to explain the embodiments of the invention. In the drawings, like reference numerals refer to like features in the various views.

#FIG. 1 is a top view of a structure at an initial fabrication stage of a processing method in accordance with embodiments of the invention.

#FIG. 2 is a cross-sectional view taken generally along line 2-2 in FIG. 1.

#With reference to FIGS. 1, 2 and in accordance with embodiments of the invention, a structure 10 for a photonic chip includes a ring resonator 12 and a waveguide core 14 having a portion disposed adjacent to a portion of the ring resonator 12. The ring resonator 12 and a waveguide core 14 may be positioned over a dielectric layer 16. In an embodiment, the dielectric layer 16 may be comprised of a dielectric material, such as silicon dioxide, that is an electrical insulator. In an embodiment, the dielectric layer 16 may be a buried oxide layer of a silicon-on-insulator substrate, and the silicon-on-insulator substrate may further include a semiconductor substrate 17 comprised of a semiconductor material (e.g., single-crystal silicon) beneath the buried oxide layer.

#In an embodiment, the ring resonator 12 may include an inner section 18 and an outer section 20 that surrounds the inner section 18. In an embodiment, the inner section 18 and the outer section 20 of the ring resonator 12 may be annular waveguide cores that are closed rings or loops, and the outer section 20 may encircle the inner section 18. The inner section 18 is bounded by an inner edge 22 and an outer edge 24 that are substantially circular. The outer section 20 is bounded by an inner edge 28 and an outer edge 30 that are substantially circular. The inner section 18 and the outer section 20 may be centered on a center 26 and therefore the inner section 18 and the outer section 20 may be concentric. The inner edge 28 of the outer section 20 is spaced outwardly from the outer edge 24 of the inner section 18 such that a slot S1 is formed therebetween as an open space having a non-linear envelope about the circumference of the ring resonator 12. In an embodiment, the inner edge 28 of the outer section 20 may have a larger radius than the outer edge 24 of the inner section 18 at any location about the circumference of the ring resonator 12.

#The inner edge 22 of the inner section 18 of the ring resonator 12 is corrugated with a series of projections 32 that protrude inwardly toward the center 26. The projections 32 are distributed about the circumference of the inner edge 22. In an embodiment, the projections 32 may be distributed with uniform spacing or pitch about the circumference of the inner edge 22. Notches 33 are formed as indentations in the inner edge 22 and the notches 33 are distributed about the circumference of the inner edge 22. The notches 33 alternate along the inner edge 22 with the projections 32. In an embodiment, the projections 32 may be rounded and the notches 33 may be rounded recesses that are indented along the inner edge 22 between adjacent pairs of projections 32.