Tunable Photonic Radiofrequency Filter with An Ultra-high Out-Of-Band Rejection

TL;DR

This paper presents a tunable photonic radiofrequency filter with a record out-of-band rejection of 80 dB, achieved through polarization control and stimulated Brillouin scattering, offering high selectivity and low insertion loss for electromagnetic applications.

Contribution

The authors demonstrate a novel active photonic RF filter with unprecedented out-of-band rejection and tunability, surpassing previous limits by integrating polarization control and stimulated Brillouin scattering.

Findings

Achieved 80 dB out-of-band rejection, 3 dB higher than previous records.

Demonstrated tunable frequency range from 2.1 to 6.1 GHz.

Provided negligible insertion loss and signal gain in the filter.

Abstract

As radiofrequency filtering plays a vital role in electromagnetic devices and systems, recently photonic techniques have been intensively studied to implement radiofrequency filters to harness wide frequency coverage, large instantaneous bandwidth, low frequency-dependent loss, flexible tunability and strong immunity to electromagnetic interference. However, one crucial challenge facing the photonic radiofrequency filter (PRF) is the less impressive out-of-band rejection. Here, to the best of our knowledge, we demonstrate a tunable PRF with a record out-of-band rejection of 80 dB, which is 3 dB higher than the maximum value (~77 dB) reported so far, when incorporating highly selective polarization control and large narrow-band amplification enabled by stimulated Brillouin scattering effect. In particular, this record rejection is arduous to be achieved for a narrow passband (e.g., a few megahertz) and a high finesse in a PRF. Moreover, the proposed PRF is an active one capable of providing negligible insertion loss and even signal gain. Tunable central frequency ranging from 2.1 to 6.1 GHz is also demonstrated. The proposed PRF will provide an ultra-high noise or clutter suppression for harsh electromagnetic scenarios, particularly when room-temperature implementation and remote distribution are needed.