Photonic integrated circuits that exploit nonlinear optics in order togenerate and process signals all-optically have achieved performance farsuperior to that possible electronically - particularly with respect to speed.We review the recent achievements based in new CMOS-compatible platforms thatare better suited than SOI for nonlinear optics, focusing on radio frequency(RF) and microwave based applications that exploit micro-resonator basedfrequency combs. We highlight their potential as well as the challenges toachieving practical solutions for many key applications. These material systemshave opened up many new capabilities such as on-chip optical frequency combgeneration and ultrafast optical pulse generation and measurement. We reviewrecent work on a photonic RF Hilbert transformer for broadband microwavein-phase and quadrature-phase generation based on an integrated frequencyoptical comb. The comb is generated using a nonlinear microring resonator basedon a CMOS compatible, high-index contrast, doped-silica glass platform. Thehigh quality and large frequency spacing of the comb enables filters with up to20 taps, allowing us to demonstrate a quadrature filter with more than a5-octave (3 dB) bandwidth and an almost uniform phase response.
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