Theoretical Investigation of Compact Intersections of Silicon Slot Waveguides

Abstract

Optical interconnection is considered as an alternative solution to electrical interconnection since the former can overcome limits of the latter. Low power consumption and high-speed data transmission are expected from optical interconnection. Matrix switches are an important element of optical interconnection, and conventional on-chip matrix switches are based on silicon strip waveguides. Since such switches are controlled by using the plasma dispersion effect, there are a few disadvantages such as the loss concomitant with the effect and limited switching speed. The disadvantages may be removed if on-chip matrix switches are constructed from silicon slot waveguides with electro-optic polymer filling their slots. This is because the electro-optic effect has better tuning properties than the plasma dispersion effect. For matrix switches based on silicon slot waveguides, intersections of silicon slot waveguides must be developed. This research theoretically investigates compact efficient intersections of silicon slot waveguides. The proposed intersection consists of mode transformers between slot waveguides and multimode strip waveguides, which are connected to a crossing of the multimode waveguides. In the mode transformer, the rails of the slot waveguide are linearly tapered to be connected to the multimode strip waveguide, and the slot is terminated within the tapering region. The mode transformer converts the slot waveguide mode into even transverse-electric (TE) modes. Because of multimode interference among the even TE modes in the crossing, the intersection can work efficiently. How to design the intersection is explained. The throughput, crosstalk, and reflectance of the intersection are –0.078 dB, –41 dB and –36 dB, respectively, at a wavelength of 1.55 μm. In the wavelength interval between 1.5 μm and 1.6 μm, the throughput is larger than –0.17 dB, the crosstalk is smaller than –40 dB, and the reflectance is smaller than –29 dB. The performance of the intersection is better than those of previous intersections of silicon slot waveguides. The footprint is 79.2 μm2, which is just less than 33 % of those of previous intersections. Finally, the fabrication tolerance of the intersection is discussed. It is demonstrated that the intersection is quite tolerable to fabrication errors.