On-chip ultra-wideband microwave photonic phase shifter and true time delay line based on a single phase-shifted waveguide Bragg grating

We propose and experimentally demonstrate a novel, ultra-broadband and continuously tunable integrated microwave photonic processor that can operate both as a RF phase shifter (PS) and a true-time-delay (TTD) line. The device is implemented with a silicon phase-shifted waveguide Bragg grating (PS-WBG) realized with a CMOS compatible process. The grating features a sharp phase shift localized within the reflection band that can be exploited in conjunction with optical single sideband modulation with full carrier (OSSB+C) to generate either PS or TTD on the modulated RF signal, depending on the relative frequency position of the carrier and the sideband with respect to the phase shift. Proof-of-concept experiments show the generation of a delay up to 25.7 ps over an 8 GHz bandwidth, and a phase shift of approx. 90 degrees over the bandwidth 16–20 GHz is also demonstrated. The phase shifter demonstration is ultimately limited by the available measurement setup, as the device is capable of providing up to 300 degrees phase shift for RF frequencies above 16 GHz over a record bandwidth approaching 1 THz.