Heterogeneous Brillouin microwave photonic filters: Towards complete photonic integration

Abstract

Microwave photonics (MWP) is a paradigm-shifting field that combines RF electronics with photonics to create RF devices with unprecedented frequency agility, owing to the broadband nature of photonic components. MWP devices that use on-chip stimulated Brillouin scattering (SBS), a nonlinear acousto-optic interaction, offer flexibility, reconfigurability and fine spectral resolution unmatched by traditional electronic or optical processing techniques. Despite the compact nature of integrated Brillouin platforms, additional active and passive optical components required to implement an MWP link are currently implemented using discrete off-chip components, introducing a bottleneck to Size, Weight and Power (SWaP) reduction. To further reduce the SWaP of Brillouin MWP processors, the requisite active and passive components and SBS waveguides must be integrated into a chip-scale platform. This thesis enhances Brillouin-based MWP filters and demonstrates the benefits of integrating onchip SBS with active and passive components. We leverage the advantages of multi-material integration by combining low-loss and reconfigurable Si3N4 MRRs with reconfigurable Brillouin processing in As2S3 waveguides to form the basis of an MWP notch filter with three independently tunable notches. Additionally, we presented an MWP bandpass filter with low loss (5 dB) and a large RF rejection ratio (40 dB), enabled by on-chip Brillouin processing and a suppressed carrier phase modulation (SCPM) scheme. Finally, we heterogeneously integrate As2S3 waveguides in an active silicon photonic platform containing E-O modulators and photodetectors, two key components of the MWP link. This platform results in dramatic SWaP reduction compared to previous Brillouin-based MWP processing systems, where the on-chip functionality was exclusively limited to generating SBS gain. We use this platform as the basis of an MWP notch filter achieving large 51 dB RF rejection, with tunability up to 15 GHz.