Electrically Tunable Topological Notch Filter for THz Integrated Photonics

Abstract

Electromagnetic filtering is essential for emerging integrated photonic technologies and widely adaptable processing of high‐bandwidth signals. The conventional electro‐optic modulator‐based photonic approach for signal filtering at microwave frequencies cannot be implemented at terahertz (THz) frequencies due to the unavailability of the THz signal‐driven optical modulator. Here, an electrically tunable on‐chip THz photonic notch filter based on the topologically protected valley hall waveguide‐cavity platform is demonstrated. The device shows a significantly large notch suppression depth of more than 20 dB with a return loss of 13 dB in the entire tuning range of notch frequency. The feedback control circuit enables precise control of the notch frequency shift with a minimum step size of 7 MHz. This work extends the application of topological photonic crystals in developing THz‐integrated photonic devices for transformative technologies, including sixth‐generation (6G) communication and high‐resolution spectral sensing.

External defect immune high quality resonances in microwave topological ring resonator

“…This property can be utilized to design a defectimmune APNF in the microwave region, which can selectively remove specific desired channels even in the presence of an external defect. To date, APNF has been proposed across various frequency regimes, such as visible [55], infrared [52,56], and THz [57]. However, a TRR-based APNF working in the microwave region would be interesting to implement in wireless communications, sensor applications, and radar systems equipped with topological protection characteristics.…”