Abstract
An ultracompact and broadband silicon-based polarization-independent power splitter is proposed by utilizing a multimode waveguide with a shallowly etched tapered slot. For input TM mode, it is divided into two beams via adiabatic mode evolution, since it cannot be well supported in the etched region, analogous to a Y-branch, and then propagates through two output channels. As to the input TE mode, unaffected by the shallowly etched slot, a twofold image is formed via self-imaging effect, corresponding to a normal multimode interference coupler, and then equally divided into two output channels. As a result, power splitting for both polarizations is realized simultaneously. Results show that there is an insertion loss of ${\lt}{0.4}\;{\rm{dB}}$ (0.2 dB) and a reflection loss of ${\lt}\; {-} {{25}}\;{\rm{dB}}$ (${-}{{35}}\;{\rm{dB}}$) for the TE (TM) polarization over the broad wavelength range of 1310 to 1870 nm, while having a device length of only 5.8 µm. Additionally, fabrication tolerances to the key structural parameters are studied in detail, and field evolution through the proposed device for both polarizations is illustrated.
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