X-shaped Photonic Crystal Waveguide with Phase-Change Materials for Non-blocking Wavelength-Selective Routing

A 2 × 2 photonic crystal (PC) wavelength router unit (WRU) is proposed. Different from traditional WRUs composed of a cross waveguide and one or two microring resonators, it only consists of a single X-shaped cross waveguide. The refractive index of four key PC rods produced with a phase-change material can be adjusted to realize a flexible optical routing function. Four WRUs of this structure are combined to realize a 4 × 4 non-blocking wavelength selective router, which has a device size of only 520 μm². As far as the non-blocking routing function is concerned, the signal-to-noise ratios (SNRs) of the 4 × 4 PC router are 19.43–23.3 dB at 1550 nm. As to the wavelength selective routing function, the 4 × 4 PC router achieves the maximum insertion loss of 0.451 dB at 1550 nm and the maximum crosstalk of −17.514 dB at 1420 nm, respectively. Not only is the device structure greatly simplified, but its size is notably reduced and the device performance is also improved. The proposed PC router unit can be easily scaled to realize a higher radix non-blocking optical routing system, which is useful in optical networks-on-chips (ONoCs).