Precise and stable synchronization between an optical frequency comb(femtosecond mode-locked laser oscillator or microresonator-based comb)and a microwave oscillator is important for various fields including telecommu-nication,radio astronomy,metrology,and ultrafast X-ray and electron science.Timing detection and synchro-nization using electro-optic sampling with an interferometer has been actively used for low-noise microwave generation,long-distance timing transfer,comb stabilization,time-of-flight sensing,and laser-microwave syn-chronization for ultrafast science facilities.Despite its outstanding performance,there has been a discrepancy in synchronization performance of more than 10 dB between the projected shot-noise-limited noise floor and the measured residual noise floor.In this work,we demonstrate the shot-noise-limited performance of an electro-optic timing detector-based comb-microwave synchronization,which enabled an unprecedented residual phase noise floor of-174.5 dBc/Hz at 8 GHz carrier frequency(i.e.,53 zs/Hz1/2 timing noise floor),integrated rms timing jitter of 88 as(1 Hz to 1 MHz),rms timing drift of 319 as over 12 h,and frequency instability of 3.6×10-20 over 10,000 s averaging time.We identified that bandpass filtering of the microwave signal and optical pulse repetition-rate multiplication are critical for achieving this performance.

CHANGMIN AHN;YONGJIN NA;MINJI HYUN;JINHO BAE;JUNGWON KIM

School of Mechanical and Aerospace Engineering,Korea Advanced Institute of Science and Technology(KAIST),Daejeon 34141,Republic of Korea

光子学研究（英文）

[1]CHANGMIN AHN;YONGJIN NA;MINJI HYUN;JINHO BAE;JUNGWON KIM-.Synchronization of an optical frequency comb and a microwave oscillator with 53 zs/Hz1/2 resolution and 10-20-level stability)[J].光子学研究（英文）,2022(02):365-372

zs,telecommu

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