Terahertz Integrated Polarization Filter Based on Slotted Bragg Grating

All-silicon substrateless integrated systems are suitable to wide-ranging terahertz applications due to their low-loss characteristics. A broadband, high-extinction level polarization filter is in demand for these on-chip systems to select the desired polarization when monomode operation of the dielectric host waveguide is required. Existing photonic designs for polarization filtering cannot cope with a large fractional bandwidth in the terahertz range. To increase the bandwidth and rejection level of the filter, a longitudinal slot is introduced into the host waveguide. Experimental validation shows a high average polarization extinction ratio of 23.5 dB between the TM and TE polarizations and an insertion loss of around 1.5 dB for the TM polarization over a 3-dB bandwidth of 87 GHz covering the whole IEEE communications band between 252 and 325 GHz. The proposed filter will be an essential component for terahertz communications to maintain the polarization purity in substrateless dielectric waveguides.