Effective-medium-clad Bragg grating filters

We propose a series of integrated Bragg grating filters with performance enhancement via the concept of effective medium. The bandstop filters are built in a high-resistivity silicon wafer and operated over the WR-3.4 band (220-330 GHz) with in-plane polarization. The proposed designs use an additional degree of freedom in controlling the effective refractive index so as to fully use the potential of the Bragg grating structures. As a result, the high insertion loss typically observed at the low-frequency bound of the filters due to weak wave confinement can be reduced, while radiation caused by the leaky-wave effect at the high-frequency bound is minimized, allowing for a 40% operation fractional bandwidth. These features are not achievable with conventional waveguide Bragg grating filters. All-silicon prototypes of filter samples are experimentally validated, demonstrating promising performance for a wide range of terahertz applications. The techniques to improve the filter characteristics by controlling the effective medium can be adopted in both microwave and optics domains. (c) 2021 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

This study introduces a series of integrated Bragg grating filters with performance enhancement by utilizing the concept of effective medium. By controlling the effective refractive index, these filters demonstrate improved performance, achieving a 40% operation fractional bandwidth. The techniques used in this study have promising applications in both microwave and optics domains.