Single-etch wide-bandwidth grating couplers with individually-tuned grating sections

A grating coupler, comprising:

• a planar waveguide;
• a first grating section comprising a first plurality of trenches etched into the planar waveguide,
• a second grating section comprising a second plurality of trenches etched into the planar waveguide,
• wherein the first plurality of trenches and the second plurality of trenches comprise a single-etch layer having a uniform depth, and wherein the first grating section is configured to scatter light of a first wavelength at a first angle relative to vertical and the second grating section is configured to scatter light of the first wavelength at a second angle relative to vertical such that light of the first wavelength is scattered by the grating coupler at a desired angle relative to vertical, and
• wherein:
• the grating coupler is optimized for a first wavelength of 1275 nm and a second wavelength of 1323 nm;
• the first grating section is configured to scatter light of the first wavelength at 11.5 degrees relative to vertical and to scatter light of the second wavelength at 7.2 degrees relative to vertical;
• the second grating section is configured to scatter light of the first wavelength at 6.7 degrees relative to vertical, and
• the combined effective scattering angle of light of the first wavelength is roughly 8 degrees relative to vertical.

An apparatus, comprising:

• a silicon substrate;
• a buried insulating layer disposed above the silicon substrate;
• a planar waveguide disposed on the buried insulating layer;
• and
• a grating coupler, comprising:
• a first grating section comprising a first plurality of trenches etched into the planar waveguide, wherein the first grating section comprises a first grating line subset and a second grating line subset, each grating line subset comprising a number of periods of the first grating section;
• and
• a second grating section comprising a second plurality of trenches etched into the planar waveguide,
• wherein the first plurality of trenches and the second plurality of trenches comprise a single-etch layer having a uniform depth, and wherein the first grating section is configured to scatter light of a first wavelength at a first angle relative to vertical and the second grating section is configured to scatter light of the first wavelength at a second angle relative to vertical such that light of the first wavelength is scattered by the grating coupler at a desired angle relative to vertical.

A grating coupler, comprising:

• a planar waveguide;
• a first grating section comprising a first plurality of trenches etched into the planar waveguide,
• a second grating section comprising a second plurality of trenches etched into the planar waveguide,
• wherein the first plurality of trenches and the second plurality of trenches comprise a single-etch layer having a uniform depth, and wherein the first grating section is configured to scatter light of a first wavelength at a first angle relative to vertical and the second grating section is configured to scatter light of the first wavelength at a second angle relative to vertical such that light of the first wavelength is scattered by the grating coupler at a desired angle relative to vertical, and
• wherein the desired angle comprises an angle at which an optical fiber is disposed above the grating coupler and relative to vertical.

A single-etch vertical grating coupler, comprising:

• a planar waveguide;
• a first grating section comprising a first plurality of trenches etched into the planar waveguide;
• and
• a second grating section comprising a second plurality of trenches etched into the planar waveguide,
• wherein the first grating section and the second grating section are optimized for multiple wavelengths, each wavelength of the multiple wavelengths associated with a user-defined weight,
• wherein the first plurality of trenches and the second plurality of trenches comprise a single-etch layer having a uniform depth, and wherein the first grating section is configured to scatter light of a first wavelength at a negative angle relative to vertical and the second grating section is configured to scatter light of the first wavelength at a positive angle relative to vertical such that light of the first wavelength is scattered in a vertical direction.

A single-etch vertical grating coupler, comprising:

• a planar waveguide;
• a first grating section comprising a first plurality of trenches etched into the planar waveguide;
• a second grating section comprising a second plurality of trenches etched into the planar waveguide,
• wherein the first plurality of trenches and the second plurality of trenches comprise a single-etch layer having a uniform depth, and wherein the first grating section is configured to scatter light of a first wavelength at a negative angle relative to vertical and the second grating section is configured to scatter light of the first wavelength at a positive angle relative to vertical such that light of the first wavelength is scattered in a vertical direction;
• and
• a silicon nitride (SiN) focusing layer disposed above the first grating section and the second grating section.