Silicon nanowire optical waveguide (SNOW)

In this paper, we propose a novel optical waveguide consisting of arrays of silicon nanowires in close proximity. We show that such a structure can guide an optical mode provided the electric field is polarized along the length of the nanowires. Furthermore, such guidance can happen even if the nanowires are arranged randomly albeit at a higher scattering loss. On the other hand, high radiation losses are observed if the electric field is polarized in the transverse direction to the nanowires. We calculate the optical radiation loss for different structures using Finite Difference Time Domain (FDTD) method. We also show that the arrayed nanowire region can be approximated using an effective index bulk waveguide. The approximation allows for design and optimization of optical structures using integrated optics methodology resulting in significant savings in time and resources. The advantage of the proposed waveguide structure is that it allows for increased optical confinement while using the enhanced optical interactions of nanowire structures compared to single nanowire photonic waveguide for diameters smaller than 100 nm. For a diameter of 50 nm for the silicon nanowire, an optical confinement factor of 33 % was achieved in the proposed waveguide as opposed to 0.1 % that is achieved for a single nanowire photonic waveguide. A radiation loss of 0.12 cm(-1) is achieved for nanowires of the same diameter spaced 75 nm apart. While our analysis is done on silicon nanowires at 1550 nm, the proposed structures can be extended to other materials and wavelength regimes also.