When silicon strip and slot waveguides are coated with a 50 nm amorphous titanium dioxide (TiO 2 ) film, measured losses at a wavelength of 1.55 μm can be as low as (2 ± 1) dB/cm and (7 ± 2) dB/cm, respectively. We use atomic layer deposition (ALD), estimate the effect of ALD growth on the surface roughness, and discuss the effect on the scattering losses. Because the gap between the rails of a slot waveguide narrows by the TiO 2 deposition, the effective slot width can be back-end controlled.

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... his is useful for precise adjustment if the slot is to be filled with, e. g., a nonlinear organic material or with a sensitizer for sensors applications.