FIELD OF THE INVENTION

The present disclosure relates to semiconductor structures and, more particularly, to grating couplers integrated with one or more airgaps and methods of manufacture.

BACKGROUND

An optical coupler is a component that couples light from an optical fiber to a waveguide structure. For example, an optical coupler can be a grating coupler used in silicon photonics to provide efficient coupling to silicon waveguides. But, the coupling efficiency of grating couplers are limited due to the light leakage into the underlying substrate.

To improve coupling efficiency, a reflector can be provided under the grating coupler to reflect light back into the waveguide structure so that the reflected light can be absorbed by the waveguide structure. For example, metallic mirrors made of noble metals, e.g., Au, or a distributed Bragg reflector (DBR) composed of vertically stacked multilayers of metal-oxides or polymer material, can be used to enhance grating coupler efficiency. However, such configurations are either incompatible with CMOS processes or require complicated fabrication steps. Hence, they cannot be easily and cost efficiently implemented on Si photonics platforms.

SUMMARY

In an aspect of the disclosure, a structure comprises: a substrate material comprising one or more airgaps; and a grating coupler disposed over the substrate material and the one or more airgaps.

In an aspect of the disclosure, a structure comprises: a bulk substrate material comprising one or more sealed airgaps within the bulk substrate material; a waveguide structure over the bulk substrate material; and a grating coupler optically coupled to the waveguide structure and disposed over the one or more airgaps.

In an aspect of the disclosure, a method comprises: forming one or more sealed airgaps in a bulk substrate material; and forming a grating coupler over the bulk substrate material and the one or more airgaps.

