Fabrication-tolerant waveguides and resonators

A method of propagating optical signals through a waveguide, the method including the steps of:

• providing an optical waveguide comprising a single core region consisting essentially of at least one material layer, each material layer consisting essentially of a material (i) substantially transparent within an operating wavelength range having a free-space center wavelength, and (ii) selected from the group consisting of a group IV semiconductor element or compound, a III-V semiconductor compound, a II-VI semiconductor compound, and silicon nitride, the single core region having a substantially rectangular cross-section with an aspect ratio of width to height selected from a range of about 1.8:1 to 3:1, the cross-section supporting at least two TE modes and only one TM mode in the operating wavelength range, and the optical waveguide having at least one TE mode with a higher effective index than the TM mode;
• and
• propagating light in the optical waveguide solely in the TM mode.