High performance photonic microwave filters based on a 50GHz optical soliton crystal Kerr micro-comb

TL;DR

This paper presents a high-performance photonic RF transversal filter utilizing a 50GHz optical soliton crystal Kerr micro-comb, achieving record low free spectral range, increased number of taps, and enhanced filtering capabilities for advanced radar and communication systems.

Contribution

The work introduces a micro-comb source with a 49 GHz free spectral range producing 80 lines, significantly improving RF filter performance and tunability over previous methods.

Findings

Achieved a QRF factor more than four times higher than previous results.

Demonstrated up to 48.9 dB out-of-band rejection with Gaussian apodization.

Realized a widely tunable center frequency and filter bandwidth.

Abstract

We demonstrate a photonic radio frequency (RF) transversal filter based on an integrated optical micro-comb source featuring a record low free spectral range of 49 GHz yielding 80 micro-comb lines across the C-band. This record-high number of taps, or wavelengths for the transversal filter results in significantly increased performance including a QRF factor more than four times higher than previous results. Further, by employing both positive and negative taps, an improved out-of-band rejection of up to 48.9 dB is demonstrated using Gaussian apodization, together with a tunable centre frequency covering the RF spectra range, with a widely tunable 3-dB bandwidth and versatile dynamically adjustable filter shapes. Our experimental results match well with theory, showing that our transversal filter is a competitive solution to implement advanced adaptive RF filters with broad operational bandwidths, high frequency selectivity, high reconfigurability, and potentially reduced cost and footprint. This approach is promising for applications in modern radar and communications systems.