Comb-Based Radio-Frequency Photonic Filters with Rapid Tunability and High Selectivity

摘要

Photonic technologies have received considerable attention for enhancement ofradio-frequency (RF) electrical systems, including high-frequency analog signaltransmission, control of phased arrays, analog-to-digital conversion, andsignal processing. Although the potential of radio-frequency photonics forimplementation of tunable electrical filters over broad RF bandwidths has beenmuch discussed, realization of programmable filters with highly selectivefilter lineshapes and rapid reconfigurability has faced significant challenges.A new approach for RF photonic filters based on frequency combs offers apotential route to simultaneous high stopband attenuation, fast tunability, andbandwidth reconfiguration. In one configuration tuning of the RF passbandfrequency is demonstrated with unprecedented (~40 ns) speed by controlling theoptical delay between combs. In a second, fixed filter configuration, cascadedfour-wave mixing simultaneously broadens and smoothes comb spectra, resultingin Gaussian RF filter lineshapes exhibiting extremely high (>60 dB) main lobeto sidelobe suppression ratio and (>70 dB) stopband attenuation.