  An integrated photonic platform with anchored-membrane structures, the
T-Guide, is proposed and numerically investigated. These compact air-clad
structures have high index contrast and are much more stable than prior
membrane-type structures. Their semi-infinite geometry enables single-mode and
single-polarization (SMSP) operation over unprecedented bandwidths. Modal
simulations quantify this behavior, showing that an SMSP window of 2.75 octaves
(1.2 - 8.1 {\mu}m) is feasible for silicon T-Guides, spanning almost the entire
transparency range of silicon. Dispersion engineering for T-Guides yields broad
regions of anomalous group velocity dispersion, rendering them a promising
platform for nonlinear applications, such as wideband frequency conversion.
