Photonic signal processing offers the advantages of large time-bandwidth capabilities to overcome inherent electronic limitations. In-fibre signal processors are inherently compatible with fibre optic microwave systems that can integrate with wireless antennas, and can provide connectivity with in-built signal conditioning and electromagnetic interference immunity. Recent methods in wideband and adaptive signal processing, which address the challenge of realising programmable microwave photonic phase shifters and true-time delay elements for phased array beamforming; ultra-wideband Hilbert transformers; single passband, widely tunable, and switchable microwave photonic filters; and ultra-wideband microwave photonic mixers, are described. In addition, a new microwave photonic mixer structure is presented, which is based on using the inherent frequency selectivity of the stimulated Brillouin scattering loss spectrum to suppress the carrier of a dual-phase modulated optical signal. Results for the new microwave photonic mixer demonstrate an extremely wide bandwidth operation of 0.2 to 20 GHz and a large conversion efficiency improvement compared to the conventional microwave photonic mixer.

A new optically controlled phased array beamforming technique based on phase modulations of wavelength-division-multiplexed (WDM) single sideband modulated light with carrier using a two-dimensional array liquid crystal on silicon (LCoS) pixels device, is presented. It realizes multiple wideband photonic microwave phase shifters, operates over a wide frequency range, and simultaneously integrates the array phase taper and the array amplitude taper within a single unit. The beamforming is software programmable. Experimental results demonstrate multiple independent microwave phase shifters that operate simultaneously over a 10-to 20-GHz frequency range, and results demonstrate beamsteering in a four-element optically controlled beam steering array at 18 GHz.Index Terms-Microwave phase shifters, microwave photonics, phased array antenna, photonic signal processing.

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A new and simple structure for a single passband microwave photonic filter is presented. It is based on using an electro-optical phase modulator and a tunable optical filter and only requires a single wavelength source and a single photodetector. Experimental results are presented that demonstrate a single passband, flat-top radio-frequency filter response without free spectral range limitations, along with the capability of tuning the center frequency and filter bandwidth independently.

Owing to its attractive optical and electronic properties, silicon carbide is an emerging platform for integrated photonics. However an integral component of the platform is missing—an electro-optic modulator, a device which encodes electrical signals onto light. As a non-centrosymmetric crystal, silicon carbide exhibits the Pockels effect, yet a modulator has not been realized since the discovery of this effect more than three decades ago. Here we design, fabricate, and demonstrate a Pockels modulator in silicon carbide. Specifically, we realize a waveguide-integrated, small form-factor, gigahertz-bandwidth modulator that operates using complementary metal-oxide-semiconductor (CMOS)-level voltages on a thin film of silicon carbide on insulator. Our device is fabricated using a CMOS foundry compatible fabrication process and features no signal degradation, no presence of photorefractive effects, and stable operation at high optical intensities (913 kW/mm2), allowing for high optical signal-to-noise ratios for modern communications. Our work unites Pockels electro-optics with a CMOS foundry compatible platform in silicon carbide.