Subwavelength Grating Waveguide Supported by a Magnetic Dipole Mode

Subwavelength grating (SWG) waveguides are attractive for building photonic integrated circuits due to their flexible dispersion engineering. These SWG waveguides are typically formed by a chain of nanoparticles with an electric dipole (ED)-like profile, which have to be nonresonant in order to homogenize the SWG waveguide as an effective strip waveguide. Here, we report the counterpart supported by the magnetic dipole (MD) mode of silicon nanoparticles. Benefiting from the special circular electric field of the MD mode, the MD-based SWG waveguide allows the construction of a tapered coupler, 90° bending waveguide, and directional coupler with more compact footprints than the counterparts composed by traditional ED-based SWG waveguides.