Ultra-wideband RF photonic phase shifter with 360° tunable phase and configurable amplitude response

We demonstrate a novel approach for implementing a broadband microwave photonic phase shifter using stimulated Brillouin scattering (SBS). This new technique solves the bandwidth limitation of previous gain-transparent SBS-based phase shifters, while achieving unprecedented minimum power fluctuations, as a function of phase shift. We introduce a new paradigm where the phase and amplitude of the optical carrier are controlled independently. This is achieved by controlling the power of two SBS pumps. The first pump is used to tune the optical carrier power, while the second is used to shift the phase of the same carrier. This additional degree of freedom enables unparalleled control of the RF amplitude and phase response of the phase shifter. We demonstrate 360° continuously tunable phase shift, with less than 0.25 dB output power fluctuations, over a frequency band from 1.5 to 31 GHz, limited only by the measurement equipment.