Grating coupler and integrated grating coupler system

Patent metadata

Field	Value
Publication number	US-11650371-B2
Application number	US-202117183013-A
Country	US
Kind code	B2
Filing date	Feb 23, 2021
Priority date	Oct 22, 2019
Publication date	May 16, 2023
Grant date	May 16, 2023

Abstract

A grating coupler having first and second ends for coupling a light beam to a waveguide of a chip includes a substrate configured to receive the light beam from the first end and transmit the light beam through the second end, the substrate having a first refractive index n1, a grating structure having curved grating lines arranged on the substrate, the grating structure having a second refractive index n1, wherein the curved grating lines have line width w and height d and are arranged by a pitch Λ, wherein the second refractive index n2 is less than first refractive index n1, and a cladding layer configured to cover the grating structure, wherein the cladding layer has a third refractive index n3. The curves of the grating lines are constructed such that the emitting beam is shaped for efficient coupling to another optical component. The curves can also be tilted to reduce coupling back into the waveguide.

First claim

What is claimed is:

1. A grating coupler having first and second ends for coupling a light beam to a waveguide of a chip comprising:
a substrate configured to receive the light beam from the first end and transmit the light beam through the second end, the substrate having a first refractive index n1;
a grating structure having grating curves arranged on the substrate, the grating structure having a second refractive index n2, wherein the grating curves have line width w and height d and are arranged by a pitch Λ, wherein the second refractive index n2 is greater than the first refractive index n1, wherein the grating curves are arranged to diffract the light beam to form a narrowing beam in a two orthogonal axes perpendicular to a light propagation direction of the light beam, wherein curves of the grating curves are constructed such that the diffracted beam is shaped for coupling to another grating coupler, wherein the grating curves are arranged as partial elliptic lines such that the partial elliptic lines form curves having protrusions toward a light propagation direction of the light beam, wherein the spacing between the lines are narrowed as a function of a distance from the end of a waveguide; and
a cladding layer configured to cover the grating structure, wherein the cladding layer has a third refractive index n3, wherein the third refractive index n3 is different from the second refractive index n2.

2. The grating coupler of claim 1 , wherein the center of the grating curves are expressed as where x and y are directions parallel to and perpendicular to the light propagation, respectively, wherein q=m,m+1,m+2 . . . (m>0) is an integer corresponding to each grating line from the first end, λ is a wavelength of the light beam, n_c is a refractive index of the substrate, ϕ_c is an angle from the waveguide surface normal, n_eff is an effective refractive index of the waveguide, Δ_x and Δ_y are coefficients of grating chirp.

3. The grating coupler of claim 1 , wherein the grating curves are arranged in an asymmetric manner with respect to a light propagation direction of the light beam, such that the reflected light from the grating curves is prevented from coupling to the first end of the waveguide.

4. The grating coupler of claim 1 , wherein the cladding layer comprises silicon dioxide.

5. The grating coupler of claim 1 , wherein the cladding layer comprises silicon nitride.

6. The grating coupler of claim 1 , wherein the cladding layer comprises polymer.

7. The grating coupler of claim 1 , wherein the cladding layer comprises the same material as the substrate.

8. The grating coupler of claim 1 , wherein the grating comprises more than two height levels.

9. The grating coupler of claim 1 , wherein a cross-sectional shape of the grating is asymmetric.

10. The grating coupler of claim 8 , wherein a rising edge of the grating is shaper than a falling edge of the grating.

11. The grating coupler of claim 1 , wherein the grating curves are arranged to be concave shapes against an input beam coming from a beam input.

12. The grating coupler of claim 1 , wherein distances between the grating curves are non-uniform.

13. The grating coupler of claim 12 , wherein the distances are arranged to decrease at a fixed rate.

14. The grating coupler of claim 1 , wherein the distance between a straight end of the first end to a first grating line is a multiple of the wavelength of the light beam in the waveguide, wherein the multiplier is between 50 and 500.

15. A grating coupler having first and second ends for coupling a light beam to a waveguide of a chip comprising:
a substrate configured to receive the light beam from the first end and transmit the light beam through the second end, the substrate having a first refractive index n1;
a grating structure having grating curves arranged on the substrate, the grating structure having a second refractive index n2, wherein the grating curves have line width w and height d and are arranged by a pitch Λ, wherein the second refractive index n2 is greater than the first refractive index n1, wherein the grating curves are arranged to diffract the light beam to form a narrowing beam in a two orthogonal axes perpendicular to a light propagation direction of the light beam, wherein curves of the grating curves are constructed such that the diffracted beam is focused on another grating coupler, wherein the grating curves are arranged as partial elliptic lines such that the partial elliptic lines form curves having protrusions toward a light propagation direction of the light beam, wherein the spacing between the lines are narrowed as a function of a distance from the end of a waveguide; and
a cladding layer configured to cover the grating structure, wherein the cladding layer has a third refractive index n3, wherein the third refractive index n3 is different from the second refractive index n2.

16. The grating coupler of claim 15 , wherein the grating curves are arranged in an asymmetric manner with respect to a light propagation direction of the light beam, such that the reflected light from the grating curves is prevented from coupling to the first end of the waveguide.

17. The grating coupler of claim 15 , wherein the cladding layer comprises silicon dioxide.

Assignees

• Mitsubishi Electric Res Laboratories Inc
• Mitsubishi Electric Corp

Inventors

• Kojima Keisuke
• Nishikawa Satoshi
• Hayashi Shusaku
• Suzuki Yosuke
• Klamkin Jonathan
• Tang Yingheng

Classifications

• G02B6/12002

  Three-dimensional structures · CPC title

• G02B6/124 Primary

  Geodesic lenses or integrated gratings · CPC title

• G02B6/34 Primary

  utilising prism or grating {(G02B6/293 takes precedence)} · CPC title