Compact design of photonic crystal ring resonator 2×2 routers as building blocks for photonic networks on chip

A highly compact 2 × 2 photonic crystal (PhC) passive wavelength router (λ-router) is proposed. The proposed λ- router exploits two photonic crystal ring resonators (PCRRs) having a 3.2 μmdiameter and a broadband PhC waveguide crossing. The router topology, allowing assembly into higher-order matrices capable of connecting multiple transmitters with multiple receivers, can be exploited as a basic building block for the design, through a compositional approach, of more complex photonic integrated networks. The design criteria, derived by applying the finite difference time domain and the plane wave expansion methods, are reported. Moreover, the analysis of a 4 × 4 λ-router configuration, obtained by assembling four 2 × 2 basic switching elements, is reported to highlight the potentiality of the basic routing element to be assembled into compact higher-order matrices that exhibit small footprints of 24 μm × 24 μm and a maximum crosstalk between the ports equal to −20.1 dB.