Compact Broadband Terahertz Filter Based on Effective Medium

Broadband filters are critical for wide communication capacity but have footprint and fabrication limitations. We present a broadband filter based on cascaded effective-medium-cladded all-silicon Bragg gratings, which has a compact size of 17 mm × 3.9 mm × 0.25 mm. The proposed design leads to a stopband covering the whole IEEE terahertz wireless communications band from 252–325 GHz with an average rejection level of 20 dB, and a passband from 220–252 GHz with the insertion loss less than -3 dB. Attributed to the introduction of a longitudinal effective-medium slot in the middle of the host waveguide, the filtering bandwidth and rejection level is significantly increased, leading to a decrease in the filter footprint and an additional degree of design flexibility compared to conventional Bragg grating filters. Such a broadband filter can be used in terahertz communication systems, terahertz sensors and other emerging terahertz technologies.