Long-range air-hole assisted subwavelength waveguides.

A novel air-hole assisted metal-dielectric-metal (MDM) waveguide is proposed and demonstrated. The configuration can be considered as a hybrid waveguide combining an MDM waveguide with a photonic crystal waveguide. The results reveal that the figure of merit of the proposed waveguide is as high as 6 × 10(8), the propagation length is 15.2 mm with the lateral mode width between 511.3 and 564.3 nm, and the waveguide isolation is over 36 dB with tiny center-to-center separation at the wavelength of 1.55 μm. In addition, we also demonstrate its broad optical bandwidth, highly efficient 90° and 120° direct bends, and low radiation loss of the metallic gaps. The above excellent features show that the proposed waveguide could be an ideal candidate for high-density photonic integrations, compared to long-range surface plasmon polariton waveguides and TE-mode MDM waveguides.