Chip-based RF Photonic Notch Filter for Deep Rejection of Multi-Band Interfering Signals

Abstract

Radio frequency (RF) filters that operate over wide frequency ranges with multiple notches are demanded by modern RF applications. Filters based on RF photonics are an attractive alternative compared to conventional RF electronic filters due to their frequency agility and tunability. However, the implementation of multi-band, high-performance notch filters has not been demonstrated due to limitations of previous filtering schemes and on-chip device performance. Here, we overcome these limitations by cascading an active on-chip Brillouin As <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> S <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> waveguide and multiple passive, low-loss Si <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> micro-ring resonators. In doing so, we produce multiple RF stopbands with frequency tunability over 20 GHz, low passband losses of 8 dB, 500 MHz 3dB bandwidth, and ultra-deep rejection exceeding 40 dB. We experimentally demonstrate the feasibility of the multi-band notch filter for both analog RF photonic filtering and image rejection for RF communication receivers.