CMOS-Compatible Fabrication of Silicon-Based Sub-100-nm Slot Waveguide With Efficient Channel-Slot Coupler

This letter presents a novel complementary metal-oxide-semiconductor (CMOS)-compatible technique to fabricate a sub-100-nm slot waveguide in wafer-scale, which is beyond the resolution limit of conventional deep ultraviolet (DUV) lithography. We also demonstrate fabrication of an efficient channel-slot coupler with an ultrasharp tip by using slanted cutting. The propagation loss of the slot waveguide obtained is similar to 11.1 +/- 1.15 dB/cm for the 100-nm slot and similar to 8.6 +/- 0.61 dB/cm for the 80-nm slot, while each 0.847 +/- 0.065 pair of channel-slot couplers has a very low insertion loss of dB. Finally, a Mach-Zehnder interferometer structure-based optical sensor demonstrates the integrate-ability of the proposed circuit.