Terahertz Integrated Polarization Rotator Based on Effective-Medium-Clad Waveguide

We propose a terahertz planar polarization rotator monolithically implemented into the all-silicon effective-medium-clad dielectric waveguide platform operating over 260-400 GHz (WR-2.8 band). The proposed polarization rotator consists of a tapered solid and an effective-medium waveguide core surrounded by in-plane asymmetric air-silicon effective-medium claddings based on mode evolution theory. The effective medium plays a key role in significantly enhancing the polarization extinction ratio over a broad bandwidth, leading to an average extinction ratio of > 15 dB over the whole WR-2.8 band with a fractional bandwidth of 42% together with an average insertion loss of < 1 dB on a footprint of 1.36 lambda(c) x 6.15 lambda(c). Such a low-loss and broadband polarization rotator is promising for beyond-5G communications with multi-dimensional multiplexing to increase channel capacities.