Vertical polarizing beamsplitter for photonics
View Patent ↗A photonic polarizing beamsplitter is disclosed. The beamsplitter comprises a first waveguide, a second waveguide located above the first waveguide, and a birefringent coupler between the first waveguide and the second waveguide. The birefringent coupler has an effective refractive index for a TM mode which is greater than a refractive index of the first waveguide, and an effective refractive index for a TE mode which is less than the refractive index of the first waveguide. The second waveguide comprises a plurality of outwardly tapering legs with a gap between adjacent legs that are connected downstream to a body. The vertical beamsplitter uses less surface area.
1. A method for making a photonic polarizing beamsplitter, comprising:
forming a first waveguide in a first optical routing layer on a substrate;
forming a birefringent coupler above the first waveguide from a birefringent material; and
forming a second waveguide in a second optical routing layer on the substrate above the first waveguide;
wherein the second waveguide comprises a plurality of outwardly tapering legs with a gap between adjacent legs that are connected downstream to a body, as determined when light is sent into the first waveguide.
2. The method of claim 1 , wherein the plurality of outwardly tapering legs has two legs or three legs.
3. The method of claim 1 , wherein a distal end of each leg has a width of 5% to 95% of a width of the first waveguide.
4. The method of claim 1 , wherein a proximal end of each leg has a width of 5% to 95% of a width of the first waveguide.
5. The method of claim 1 , wherein each gap has a width of 5% to 95% of a width of the first waveguide.
6. The method of claim 1 , wherein a downstream end of the body has width of 30 to 300% of a width of the first waveguide.
7. The method of claim 1 , wherein the first waveguide has a width of about 0.1 micrometers to about 20 micrometers, or wherein the first waveguide has a length of about 1 micrometer to about 50 micrometers.
8. The method of claim 1 , wherein the second waveguide further comprises an inwardly tapering head downstream of the body.
9. The method of claim 8 , wherein a downstream end of the head has a width of 30% to 300% of the first waveguide, and wherein the downstream end width of the head is less than a width of a downstream end of the body.
10. The method of claim 9 , wherein the head has a length of about 1 micrometer to about 50 micrometers.
11. The method of claim 1 , wherein the second waveguide is in the form of a Bragg grating.
12. The method of claim 11 , wherein the Bragg grating has a grating period of about 50 nanometers to about 600 nanometers.
13. The method of claim 12 , wherein a proximal end region of each leg includes a quadrilateral feature.
14. The method of claim 13 , wherein an upstream end of the quadrilateral feature has a width of about 10 nanometers to about 300 nanometers.
15. The method of claim 12 , wherein the Bragg grating has a spacing of 1% to 99% of a grating period of the Bragg grating.
16. The method of claim 1 , wherein the birefringent coupler has an effective refractive index for a TM mode which is greater than a refractive index of the first waveguide, and wherein the birefringent coupler has an effective refractive index for a TE mode which is less than the refractive index of the first waveguide.
17. A photonic polarizing beamsplitter, comprising:
a first waveguide;
a second waveguide located above the first waveguide; and
a birefringent coupler between the first waveguide and the second waveguide;
wherein the second waveguide comprises a plurality of outwardly tapering legs with a gap between adjacent legs that are connected downstream to a body, as determined when light is sent into the first waveguide.
18. The beamsplitter of claim 17 , wherein the birefringent coupler comprises hafnium oxide, zirconium oxide, aluminum oxide, hafnium silicate, zirconium silicate, hafnium oxynitride, zirconium oxynitride, silicon oxynitride, boron nitride, or silicon carbide.
19. A method for separating TE-mode wavelengths from TM-mode wavelengths in a photonic device, comprising:
sending an optical input into a first waveguide, the optical input comprising the TE-mode wavelengths and the TM-mode wavelengths;
passing the optical input through a vertical overlap region that includes a birefringent coupler and a second waveguide above the first waveguide, wherein the second waveguide comprises a plurality of outwardly tapering legs with a gap between adjacent legs that are connected downstream to a body;
receiving the TM-mode wavelengths in the second waveguide; and
retaining the TE-mode wavelengths in the first waveguide.
20. The method of claim 19 , wherein the body has a length of about 1 micrometer to about 50 micrometers.