Low-loss waveguide transition
View Patent ↗A waveguide device that includes a first waveguide, a second waveguide and a transition region. The first waveguide has a first height and the second waveguide has a second height different from the first height. The transition region is between the first waveguide and the second waveguide and includes an asymmetrical taper of the first waveguide.
1. A waveguide device comprising:
a first waveguide with a first height;
a second waveguide with a second height different from the first height; and
a transition region between the first waveguide and the second waveguide, the transition region comprising a first asymmetrical taper of the first waveguide, the first asymmetrical taper being formed from a single edge extending between opposed first and second sides of the first waveguide;
wherein the second waveguide has a second asymmetrical taper, the second asymmetrical taper having an edge that is co-linear with and parallel to the first side of the first waveguide.
2. The waveguide device of claim 1 , wherein the first height and the second height is along a first direction, and the first asymmetrical taper is asymmetric about an imaginary plane that bisects a width of the first waveguide, wherein the width of the first waveguide is along a second direction perpendicular to the first direction.
3. The waveguide device of claim 1 , wherein the first waveguide is configured to support a first optical mode and the second waveguide is configured to support a second optical mode, the first and second optical modes being polarized along a common polarization direction.
4. The waveguide device of claim 1 , wherein the transition region comprises a transition tip with a width less than 50 nm.
5. The waveguide device of claim 1 , wherein the second waveguide has a first width at the transition region and a second width a first distance from the transition region, wherein the first width is greater than the second width.
6. The waveguide device of claim 1 , wherein the second asymmetrical taper begins at the transition region.
7. The waveguide device of claim 1 , wherein the first waveguide has a transverse width that supports only a first mode in a TE polarization and a second mode in a TM polarization at an operational wavelength.
8. The waveguide device of claim 1 , wherein the first waveguide is formed from silicon.
9. The waveguide device of claim 1 , wherein the waveguide device is monolithic.
10. A method comprising:
receiving light within a first waveguide of a photonic chip, wherein the first waveguide has a first height;
transitioning the light from the first waveguide to a second waveguide of the photonic chip using a first asymmetrical taper of the first waveguide, wherein the second waveguide has a second height different from the first height, wherein the first asymmetrical taper is formed from a single edge extending between opposed first and second sides of the first waveguide, and wherein the second waveguide has a second asymmetrical taper, the second asymmetrical taper having an edge that is co-linear with and parallel to the first side of the first waveguide.
11. The method of claim 10 , wherein the first height and the second height is along a first direction, and the first asymmetrical taper is asymmetric about an imaginary plane that bisects a width of the first waveguide, wherein the width of the first waveguide is along a second direction perpendicular to the first direction.
12. The method of claim 10 , wherein the light is polarized along a polarization direction within the first waveguide and is polarized along the polarization direction within the second waveguide.
13. The method of claim 10 , further comprising:
changing a transverse mode size of the light as it propagates through the second waveguide.
14. The method of claim 10 , further comprising:
outputting the light from the second waveguide; and
receiving the light at an optical fiber.