Optical performance of long-range air-gaps assisted subwavelength waveguides

A long-range air-gaps assisted subwavelength waveguide is proposed and demonstrated. The configuration can be interpreted as a combination of a silicon waveguide and a metal-dielectric-metal (MDM) waveguide. Unlike the conventional MDM waveguide, the proposed waveguide is polarization insensitive because long propagation lengths can be achieved by both the transverse electric (TE) and transverse magnetic (TM) polarizations. The propagation length of this waveguide can even be up to decimeters. Moreover, this design is very compact with only a 1.05 mu m center-to-center separation between two adjacent waveguides, while the waveguide isolation is >58 dB. Also, it is capable of guiding light effectively (>97% transmittance) through a 90 deg bend with a small bending radius (1 mu m). These unique features make the proposed waveguide a promising candidate for the future large-scale photonic integrated circuits. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)