In a recent study, scientists in China describe a metal-dielectric-metal (MDM)-photonic crystal (PC)-hybrid waveguide with promising characteristics. The configuration, dubbed a long-range air-hole assisted subwavelength (LR-AHAS) waveguide, can be considered as the equivalent combination of a MDM waveguide with a PC waveguide.

By taking full advantage of the ultra-low propagation loss of a PC waveguide, the high-absorptive metal can be partly isolated, and the loss of the hybrid waveguide can be significantly reduced. Meanwhile, by utilizing the high reflectivity with the mirror symmetry of a metal as well as the strong mode confinement of a MDM structure resulting from the evanescent field effect, the lateral periodic number and the entire width of a PC waveguide can be largely decreased.

Simulation and testing

The results reveal that the figure of merit (FOM) of the proposed waveguide is as high as 6 × 108, the propagation length is 15.2 mm with a lateral mode width of between 511.3 nm and 564.3 nm, and waveguide isolation of over 36 dB with tiny centre-to-centre separation at the wavelength of 1.55 µm. In addition, broad optical bandwidth, high efficiency 90° and 120° direct bends, and low radiation loss of the metallic gaps in the new waveguide are also demonstrated.

These excellent features show that the proposed waveguide could be an ideal candidate for high-density photonic integrations.

Full details can be found in the journal Nanotechnology 24 235203.

Further reading

Hybrid plasmon-waveguide mode improves the sensitivity of plasmonic nanosensors (Jul 2012)
Short- and long-range SPP waveguides detect xylene (May 2013)
Self-perfection by liquefaction shrinks waveguide loss (Aug 2009)
Narrow waveguide strengthens optical trap (Jan 2009)
Nanowires light up photonic crystal waveguides (Sep 2008)