Acid block for hybrid silicon device processing compatible with low-loss waveguides

A hybrid optical device, comprising:

• a silicon-on-insulator substrate comprising at least one waveguide, the waveguide comprising a rib structure between a first waveguide channel and a second waveguide channel, the first waveguide channel comprising a first sidewall and a second sidewall, the first sidewall of the first waveguide channel comprising a sidewall of the rib structure, the rib structure comprising a first end and a second end, light entering the rib structure at the first end propagates along the rib structure and exits the rib structure at the second end, the rib structure comprising a length extending in a first direction along the rib structure and a width extending in a direction that is substantially perpendicular to the length, and at least one fin structure formed between the first sidewall and the second sidewall of the first waveguide channel and comprising a width that extends substantially in a same direction as the width of the rib structure, the second waveguide channel comprising a first sidewall and a second sidewall, the first sidewall of the second waveguide channel comprising a sidewall of the rib structure, and at least one fin structure formed between the first sidewall and the second sidewall of the second waveguide channel, the at least one fin structure in the second waveguide channel corresponding to the fin structure in the first waveguide channel and comprising a width that extends substantially in a same direction as the width of the rib structure, the at least one fin structure in the first waveguide channel and the corresponding fin structure in the second waveguide channel together comprising an optical loss that is less than or equal to about 1.4 dB for a rib structure width that is less than or equal to about 1.80 μm and a fin structure width that is less than or equal to about 2.0 μm;
• and
• a III-V die bonded to the silicon-on-insulator substrate, the III-IV die comprising circuitry coupled to at least one waveguide.

A device, comprising:

• a waveguide comprising a rib structure between a first waveguide channel and a second waveguide channel, the rib structure comprising a length extending in a first direction along the rib structure and a width extending in a direction that is substantially perpendicular to the length, the first waveguide channel comprising a first sidewall and a second sidewall, the first sidewall of the first waveguide channel comprising a sidewall of the rib structure, the second waveguide channel comprising a first sidewall and a second sidewall, the first sidewall of the second waveguide channel comprising a sidewall of the rib structure;
• at least one fin structure formed between the first sidewall and the second sidewall of the first waveguide channel, the at least one fin structure formed between the first sidewall and the second sidewall of the first waveguide channel comprising a height that is substantially equal to a height of the first sidewall and the second sidewall, and comprising a width that extends substantially in a same direction as the width of the rib structure;
• and
• at least one fin structure formed between the first sidewall and the second sidewall of the second waveguide channel, the at least one fin structure formed between the first sidewall and the second sidewall of the second waveguide channel comprising a height that is substantially equal to a height of the first sidewall and the second sidewall of the second waveguide channel, and comprising a width that extends substantially in a same direction as the width of the rib structure,
• a fin structure in the second waveguide channel corresponding to the fin structure in the first waveguide channel, and the fin structure in the first waveguide channel and the corresponding fin structure in the second waveguide channel together comprising an optical loss that is less than or equal to about 1.4 dB for a rib structure width that is less than or equal to about 1.80 μm and a fin structure width that is less than or equal to about 2.0 μm.