Reconfigurable and frequency-agile on-chip microwave photonic bandpass and bandstop filters using stimulated Brillouin scattering

In this paper, we present our recent results in the area of microwave photonics. Integrated microwave photonic bandpass and bandstop filters were realized using stimulated Brillouin scattering (SBS). Our recent breakthrough in the fabrication of chalcogenide waveguides has allowed us to achieve an on-chip SBS gain of >40 dB, enabling for the first time the tailoring of the SBS response well beyond the intrinsic linewidth (~30 MHz). An electrical comb generated by an arbitrary waveform generator was modulated onto an optical carrier to generate a broadened pump which via the SBS effect created a flat and rectangular bandpass filter response in the RF domain. Controlling the number of pump lines allowed bandwidth reconfigurability from 30 MHz to 440 MHz. The measured selectivity and the passband ripple were >20 dB and <1.9 dB, respectively and the center frequency of the filter was tuned up to 30 GHz. A bandstop filter response was realized by using a novel RF interferometry technique via accurate control of the amplitude and phase of the sidebands of the modulated probe. The bandwidth was reconfigurable from 75 MHz-300 MHz and the central frequency of the filter was tunable up to 30 GHz.