A compact time delay unit is fundamental to integrated photonic circuits with applications in,for example,op-tical beam-forming networks,photonic equalization,and finite and infinite impulse response optical filtering.In this paper,we report a novel gain-enabled delay readout system using a tunable optical carrier,low-frequency RF signal and CMOS-compatible photodetectors,suitable for silicon photonic integration.The characterization method relies on direct phase measurement of an input RF signal and thereafter extraction of the delay profile.Both integrated silicon and germanium photodetectors coupled with low-bandwidth electronics are used to characterize a microring resonator-based,true-time delay unit under distinct ring-bus coupling formats.The detectors,used in both linear and avalanche mode,are shown to be successful as optical-to-electrical converters and RF amplifiers without introducing significant phase distortion.For a Si-Ge separate-absorption-charge-multiplication avalanche detector,an RF amplification of 10 dB is observed relative to a Ge PIN linear detector.An all-silicon defect-mediated avalanche photodetector is shown to have a 3 dB RF amplification compared to the same PIN detector.All ring delay measurement results are validated by full-wave simulation.Additionally,the impact of photodetector biasing and system linearity is analyzed.

RANJAN DAS;YANRAN XIE;HENRY FRANKIS;KERU CHEN;HERMANN RUFENACHT;GUILLAUME LAMONTAGNE;JONATHAN D.B.BRADLEY;ANDREW P.KNIGHTS

Department of Engineering Physics,McMaster University,Hamilton,Ontario L8S 4L7,Canada;McDonald Detwiler Associates,Sainte-Anne-de-Bellevue,Quebec H9X 3R2,Canada

光子学研究（英文）

[1]RANJAN DAS;YANRAN XIE;HENRY FRANKIS;KERU CHEN;HERMANN RUFENACHT;GUILLAUME LAMONTAGNE;JONATHAN D.B.BRADLEY;ANDREW P.KNIGHTS-.Gain-enabled optical delay readout unit using CMOS-compatible avalanche photodetectors)[J].光子学研究（英文）,2022(10):2422-2433

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