Systems and methods for photonic polarization rotators
An integrated non-reciprocal polarization rotator comprises a substrate, a Faraday crystal, a first waveguide, and a second waveguide. The substrate has a recess extending to a predetermined depth. The Faraday crystal is mounted in the recess and optically coupled with the first waveguide and the second waveguide.
1. A photonic device comprising:
a substrate having a support surface and a device surface opposing the support surface, thereby defining a substrate thickness, wherein the substrate includes a fill region;
a Faraday crystal mounted in the fill region and having a first facet and a second facet opposing the first facet;
a first waveguide integrated on the substrate and optically coupled with the first facet of the Faraday crystal;
an index matching region disposed between the first waveguide and the first facet of the Faraday crystal; and
a second waveguide integrated on the substrate and optically coupled with the second facet of the Faraday crystal, wherein:
the Faraday crystal is a first Faraday crystal;
the fill region is a first fill region; and
the photonic device further comprises:
a second fill region in the substrate;
a second Faraday crystal mounted in the second fill region, the second Faraday crystal having a first facet and a second facet opposing the first facet;
a third waveguide integrated on the substrate and coupled with the first facet of the second Faraday crystal;
a fourth waveguide integrated on the substrate and coupled with the second facet of the second Faraday crystal;
a first beam splitter integrated on the substrate; and
a second beam splitter integrated on the substrate;
the first waveguide and the third waveguide are coupled with the first beam splitter; and
the second waveguide and the fourth waveguide are coupled with the second beam splitter.
2. The photonic device of claim 1 , wherein the index matching region is a first index matching region and the photonic device further comprises a second index matching region disposed between the second waveguide and the second facet of the Faraday crystal.
3. The photonic device of claim 1 wherein the Faraday crystal is permanently polled.
4. The photonic device of claim 3 wherein the Faraday crystal comprises at least one of bismuth europium holmium gallium iron garnet or bismuth yttrium iron garnet.
5. The photonic device of claim 1 wherein the Faraday crystal comprises yttrium iron garnet or bismuth-doped iron garnet.
6. The photonic device of claim 5 further comprising a magnet.
7. The photonic device of claim 1 wherein the substrate comprises silicon.
8. The photonic device of claim 7 further comprising an insulating layer disposed between the substrate and the first waveguide; and between the substrate and the second waveguide.
9. The photonic device of claim 8 further comprising an amorphous silicon layer disposed between the insulating layer and the Faraday crystal.
10. The photonic device of claim 1 , wherein the first beam splitter, the second beam splitter, or both the first beam splitter and the second beam splitter are polarizing beam splitters.
11. The photonic device of claim 1 , the photonic device further comprising a reciprocal polarization rotator, wherein:
the reciprocal polarization rotator is between the first waveguide and the first beam splitter; and
the reciprocal polarization rotator is integrated on the substrate.
12. The photonic device of claim 1 , wherein:
the first beam splitter is further coupled with a fifth waveguide;
the fifth waveguide is integrated on the substrate; and
the fifth waveguide is an input port.
13. The photonic device of claim 1 , the photonic device further comprising:
a first reciprocal polarization rotator, wherein:
the first reciprocal polarization rotator is between the first waveguide and the first beam splitter; and
the first reciprocal polarization rotator is integrated on the substrate; and
a second reciprocal polarization rotator, wherein:
the second reciprocal polarization rotator is between the third waveguide and the first beam splitter; and
the second reciprocal polarization rotator is integrated on the substrate.
14. The photonic device of claim 13 , wherein:
the first reciprocal polarization rotator, the first waveguide, the first Faraday crystal, and the second waveguide are on a first optical path between the first beam splitter and the second beam splitter; and
the second reciprocal polarization rotator, the third waveguide, the second Faraday crystal, and the fourth waveguide are on a second optical path between the first beam splitter and the second beam splitter.