Heterogeneous waveguide integrated optical isolator and circulator
Embodiments of the invention utilize optical structures created by processes in the wafer fabrication foundry to form optical isolators and circulators. Grating coupling structures are utilized to couple light having a chosen polarization component into free space through non-reciprocal rotation material; said light is captured by another set of grating coupling structures after experiencing a 45 degree rotation of the polarization. By non-reciprocally rotating the polarization, the input and output ports of the optical isolator will be different depending on the direction of the light propagation. The amount of non-reciprocal rotation material utilized by embodiments of the invention may be small, and the grating coupling structures may be efficiently made to couple to each other as their field profiles may be matched and their position may be precisely defined by lithographic means.
1. An optical isolator comprising:
a two dimensional (2D) grating coupler comprising first and second waveguides and first and second corresponding gratings, the first grating coupler to direct light having a first polarization component from the first waveguide, the second grating coupler to direct light having a second polarization component that is orthogonal to the first polarization component to the second waveguide;
a polarization rotator comprising a rotation angle of 45 degrees in a principle direction;
a polarizer configured to pass light having a polarization state of the first polarization state rotated 45 degrees in the principle direction; and
an optical coupler to receive light of a first polarization state from the first waveguide and to transmit light of a second polarization state to the second waveguide.
2. The optical isolator of claim 1 , wherein the polarization rotator comprises a non-reciprocal faraday rotator.
3. The optical isolator of claim 1 , wherein the polarization rotator comprises a quarter-wave plate.
4. The optical isolator of claim 1 , wherein the optical coupler comprises an optical fiber.
5. The optical isolator of claim 1 , wherein the optical coupler comprises a lens.
6. An optical isolator comprising:
a first waveguide;
a second waveguide;
a first grating coupler to direct light having a first polarization component from the first waveguide;
a second grating coupler, separate from the first grating coupler, to direct light having a second polarization component to the second waveguide, wherein the second polarization component comprises a polarization axis oriented at 45 degrees relative to the first polarization component in a principle direction; and
a non-reciprocal rotator to rotate light received from the first grating coupler, at a first surface, 45 degrees relative to the first polarization component in a principle direction, wherein the second grating coupler is to receive the rotated light.
7. The optical isolator of claim 6 , wherein the non-reciprocal rotator comprises a rotation angle of 22.5 degrees in the principle direction, and the optical isolator further comprises:
a reflector disposed on a second surface of the non-reciprocal rotator to reflect light opposite the first surface of the non-reciprocal rotator.
8. The optical isolator of claim 6 , wherein the non-reciprocal rotator comprises a rotation angle of 45 degrees in the principle direction, and the second grating coupler is disposed on a second surface of the non-reciprocal rotator to reflect light opposite the first surface of the non-reciprocal rotator.
9. The optical isolator of claim 8 , wherein the non-reciprocal rotator comprises a quarter wave plate.
10. The optical isolator of claim 6 , wherein the non-reciprocal rotator comprises a faraday rotator.
11. An optical circulator comprising:
a plurality of two-dimensional grating couplers; and
a non-reciprocal polarization rotator comprising a rotation angle of 45 degrees in a principle direction;
wherein the plurality of two-dimensional (2D) grating couplers are to exchange light via the non-reciprocal polarization rotator, and wherein each of the plurality of two-dimensional grating couplers comprises:
first and second waveguides and first and second corresponding gratings, the first grating coupler to direct light having a first polarization component from the first waveguide, the second grating coupler to direct light having a second polarization component that is orthogonal to the first polarization component to the second waveguide.
12. The optical circulator of claim 11 , wherein the plurality of 2D grating couplers are disposed on a first surface of the non-reciprocal rotator, wherein the non-reciprocal rotator comprises a rotation angle of 22.5 degrees in the principle direction, and the optical circulator further comprises:
a reflector disposed on a second surface of the non-reciprocal rotator to reflect light opposite the first surface of the non-reciprocal rotator.
13. The optical circulator of claim 11 , wherein the non-reciprocal rotator comprises a rotation angle of 45 degrees in the principle direction, and the plurality of 2D grating couplers comprises first and second grating couplers disposed on opposing surfaces of the non-reciprocal rotator.
14. The optical circulator of claim 13 , wherein the non-reciprocal rotator comprises a quarter wave plate.
15. The optical circulator of claim 11 , wherein the non-reciprocal rotator comprises a faraday rotator.