A subwavelength silicon photonic wire integrated with three-dimensional (3D) tapered couplers fabricated through self-profile transformation is presented. Unlike the conventional process of defining the silicon wire by etching, the profile transformation, which is induced by surface diffusion of silicon atoms during hydrogen annealing, is applied on as-etch silicon structures to make photonic wires. Additionally, this process is able to reduce sidewall roughness to be less than 1nm, substantially meliorating the unwanted scattering loss. Exploiting this technology, the authors demonstrated that the photonic wire has low propagation loss of 1.26dB∕cm and the 3D tapered coupler has coupling efficiency of 54%.

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A novel low-loss silicon wire waveguide as well as 3-D tapered couplers is demonstrated by self profile transformation for the first time. The preliminary experimental results show the propagation loss is 2 dB/cm and the coupler loss is 2.7 dB.