Ultra Compact Nanoplasmonic Dual-Band Filters with Tunable Silica Stubs for Nanoscale Networks

This article presents the design and analysis of a dual- band pass filter (BPF) with a single plasmonic circular ring resonator (CRR) using a metal-insulator-metal (MIM) guiding structure. The most distinctive feature of the designed resonator is that the first and second-order degenerate modes operate concurrently at two simultaneous pass bands at corresponding wavelengths of 1300 nm and 1600 nm, respectively. Firstly, the basic characteristics of the MIM waveguide are studied and analyzed using full-wave analysis. Secondly, to design the filter structure, four and eight open-end silica <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\textbf{SiO}_{2})$</tex> stubs are added symmetrically to the single CRR with separations of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$135^{\circ}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$45^{\circ}$</tex>. This provides synchronous excitation of two transmission peaks in the second passband, which is currently a desirable feature in many applications. The second stub, with 450 separations, exhibits much better performance at frequencies lower than the first pass-band and in between the two passbands. Hence, this filter will be very useful in silicon photonic integrated circuits (SPICs) where a dual pass-band is required.