Heterogeneously integrated electro-optic modulator
In an electro-optical modulator, an electro-optical modulation layer is bonded to a cladding layer that overlies a substrate. A modulation zone waveguide is optically coupled to the electro-optical modulation layer and optically coupled to an I/O waveguiding structure embedded in the cladding layer. The I/O waveguiding structure is conformed to guide input light toward the modulation zone waveguide and to guide output light away from the modulation zone waveguide.
1. An electro-optical modulator apparatus, comprising:
a substrate;
a cladding layer that overlies the substrate;
an EO modulation layer bonded to the cladding layer;
a modulation zone waveguide optically coupled to the EO modulation layer; and
an I/O waveguiding structure embedded in the cladding layer at a separation from the EO modulation layer such that the EO modulation layer is nearer to the modulation zone waveguide than it is to the I/O waveguiding structure, wherein:
the I/O waveguiding structure is optically coupled to the modulation zone waveguide; and
the I/O waveguiding structure is conformed to guide input light toward the modulation zone waveguide and to guide output light away from the modulation zone waveguide.
2. The apparatus of claim 1 , wherein the modulation zone waveguide is a single-mode waveguide and the I/O waveguiding structure comprises at least one single-mode waveguide.
3. The apparatus of claim 1 , wherein the modulation zone waveguide and the I/O waveguiding structure are included in an arm of a Mach-Zehnder modulator.
4. The apparatus of claim 1 , further comprising radio-frequency electrodes that are electromagnetically coupled to the EO modulation layer.
5. The apparatus of claim 4 , wherein the radio-frequency electrodes are traveling wave radio-frequency electrodes.
6. The apparatus of claim 4 , wherein the radio-frequency electrodes are coplanar.
7. The apparatus of claim 4 , wherein the radio-frequency electrodes are buried within the cladding layer.
8. The apparatus of claim 4 , wherein the radio-frequency electrodes are buried within the cladding layer at a greater depth than the I/O waveguiding structure.
9. The apparatus of claim 1 , wherein:
the substrate comprises a silicon or SOI wafer; and
the modulation zone waveguide and the I/O waveguiding structure are embedded in a cladding layer of silicon dioxide.
10. The apparatus of claim 1 , wherein the I/O waveguiding structure has an input portion conformed to couple guided light into the modulation zone waveguide, and an output portion conformed to couple light out of the modulation zone waveguide.
11. The apparatus of claim 1 , wherein the EO modulation layer comprises lithium niobate.
12. The apparatus of claim 1 , wherein the EO modulation layer comprises thin film lithium niobate less than 1 μm in thickness.
13. The apparatus of claim 1 , wherein the EO modulation layer is conformed as a layer less than one operating wavelength in thickness.
14. The apparatus of claim 1 , wherein the I/O waveguiding structure comprises a waveguide with a tapered end for coupling guided light into the modulation zone waveguide.
15. The apparatus of claim 1 , wherein the I/O waveguiding structure comprises a waveguide with a tapered end for coupling guided light out of the modulation zone waveguide.
16. The apparatus of claim 1 , wherein the I/O waveguiding structure is situated more deeply within the cladding layer than the modulation zone waveguide, and the optical coupling between said structure and said waveguide is vertical optical coupling.
17. The apparatus of claim 1 , wherein a silicon device layer is defined in the substrate.
18. The apparatus of claim 17 , wherein one or more active electronic devices are defined in the silicon device layer.
19. The apparatus of claim 17 , wherein one or more silicon photonic devices are defined in the silicon device layer.
20. The apparatus of claim 17 , wherein the I/O waveguiding structure and the modulation zone waveguide comprise silicon nitride waveguides.