Integrated photonics mode expander

A method of fabricating a waveguide mode expander, the method comprising:

• providing a silicon on insulator (SOI) substrate comprising a waveguide, wherein:
• the waveguide defines a waveguide thickness and terminates at an output end, and
• the waveguide supports an optical mode of an initial mode size at the output end;
• forming a mounting region adjacent the output end of the waveguide;
• providing a multi-layer chiplet comprising one or more optical materials, wherein:
• a lower layer of the chiplet comprises a metal layer,
• a first layer of the one or more optical materials defines a first layer thickness that supports an input optical mode size substantially the same size as the initial mode size, and
• one or more overlying layers define thicknesses that, when combined with the first layer, support an output optical mode size that is larger than the initial mode size;
• bonding the chiplet in the mounting region, wherein bonding the chiplet comprises forming a metal to semiconductor bond with the SOI substrate;
• and
• selectively removing portions of the chiplet to form tapered stages that successively increase in number and lateral size from a proximal end of the chiplet adjacent the waveguide, to a distal end of the chiplet, each tapered stage being formed of a portion of a respective layer of the multi-layer chiplet,
• such that the first layer and the tapered stages form a waveguide mode expander that adiabatically expands an optical mode of light traversing the chiplet, from the initial optical mode size entering the proximal end, to the output optical mode size at the distal end.

A method of fabricating a waveguide mode expander, the method comprising:

• providing a silicon on insulator (SOI) substrate comprising a waveguide, wherein:
• the waveguide defines a waveguide thickness and terminates at an output end, and
• the waveguide supports an optical mode of an initial mode size at the output end;
• forming a mounting region adjacent the output end of the waveguide;
• providing a multi-layer chiplet comprising one or more optical materials, wherein
• a first layer of the one or more optical materials defines a first layer thickness that supports an input optical mode size substantially the same size as the initial mode size, and
• one or more overlying layers define thicknesses that, when combined with the first layer, support an output optical mode size that is larger than the initial mode size, and wherein providing the multi-layer chiplet comprises:
• successively depositing the first layer and the one or more overlying layers on a substrate;
• and
• singulating the substrate to form multiple ones of the chiplet;
• bonding the chiplet in the mounting region;
• and
• selectively removing portions of the chiplet to form tapered stages that successively increase in number and lateral size from a proximal end of the chiplet adjacent the waveguide, to a distal end of the chiplet, each tapered stage being formed of a portion of a respective layer of the multi-layer chiplet,
• such that the first layer and the tapered stages form a waveguide mode expander that adiabatically expands an optical mode of light traversing the chiplet, from the initial optical mode size entering the proximal end, to the output optical mode size at the distal end.

A method of coupling a first waveguide with a second waveguide, the method comprising:

• providing a silicon on insulator (SOI) substrate comprising the first waveguide and the second waveguide, wherein:
• the first waveguide defines a first waveguide thickness and terminates at an output end,
• the first waveguide supports a first optical mode of an initial mode size at the output end,
• the second waveguide defines a second waveguide thickness and terminates at an input end,
• the second waveguide supports a second optical mode of a final mode size at the input end, the final mode size being greater than or equal to the initial mode size;
• forming a mounting region between the output end of the first waveguide and the input end of the second waveguide;
• providing a multi-layer chiplet comprising one or more optical materials, wherein
• a first layer of the one or more optical materials defines a first layer thickness that supports an input optical mode size substantially the same size as the initial mode size, and
• one or more overlying layers define thicknesses that, when combined with the first layer, support an output optical mode size that is substantially the same size as the final mode size;
• bonding the chiplet in the mounting region;
• and
• selectively removing portions of the chiplet to form tapered stages that successively increase in number and lateral size from a proximal end of the chiplet adjacent the first waveguide, to a distal end of the chiplet adjacent the second waveguide, each tapered stage being formed of a portion of a respective layer of the multi-layer chiplet,
• such that the first layer and the tapered stages form a waveguide mode expander that adiabatically expands an optical mode of light traversing the chiplet, from the initial mode size entering the proximal end, to the output optical mode size at the distal end.