An all-silicon, single-mode Bragg cladding rib waveguide

In this paper, we demonstrate a direct method of fabricating an all-silicon, single-mode Bragg cladding rib waveguide using proton beam irradiation and subsequent electrochemical etching. The Bragg waveguide consists of porous silicon layers with a low index core of 1.4 that is bounded by eight bilayers of alternating high and low refractive index of 1.4 and 2.4. Here, the ion irradiation acts to reduce the thickness of porous silicon formed, creating an optical barrier needed for lateral confinement. Single-mode guiding with losses as low as approximately 1 dB/cm were obtained for both TE and TM polarization over a broad range of wavelengths from 1525 nm to 1625 nm. Such an approach offers a method for monolithic integration of Bragg waveguides in silicon, without the need for multiple processes of depositing alternating materials.