Experimental Demonstration of Time-Delay Interferometry with Optical Frequency Comb

Heterodyne laser phase measurements in the Laser Interferometer Space Antenna (LISA) aredegraded by the phase uctuations of the onboard clocks, resulting in unacceptable sensitivity performancelevels of the interferometric data. The current scheme for cancellation of the clock phasenoise requires 1 GHz modulation of the ranging laser beams and additional inter-spacecraft clockrecovery heterodyne phase measurements. Here we report experimental results for an alternativeapproach to clock noise cancellation based on modied second generation time-delay interferometry(TDI) with optical frequency combs (OFCs). The use of OFCs in the LISA scheme allowssimultaneous cancellation of both laser and clock noises, and would eliminate the need for 1 GHzlaser modulations and associated demodulation detections. Two Mach-Zehnder interferometers withacousto-optic modulators were used to simulate two LISA arms with Doppler shifts and time delays.With a self-referenced OFC locked to the laser providing the clock signal, we achieve simultaneoussuppression of laser and clock noises by 7 and 1.5 orders of magnitudes respectively down to the setupnoise oor. Based on a numerical analysis, we further show that the noise suppression performanceof the OFC-based TDI scheme can meet the LISA mission requirements with ample margin.激光干涉空间天线（Laser Interferometer Space Antenna, LISA）的外差激光相位测量会受到星载时钟相位涨落的劣化，导致干涉数据的灵敏度性能降至无法接受的水平。当前用于抵消时钟相位噪声的方案，需要对测距激光束施加1吉赫兹调制，并开展额外的航天器间时钟恢复外差相位测量。本文报道了一种基于改进型第二代时延干涉仪（time-delay interferometry, TDI）与光学频率梳（optical frequency combs, OFCs）的时钟噪声抵消替代方案的实验结果。将光学频率梳应用于LISA方案中，可同时抑制激光噪声与时钟噪声，且无需进行1吉赫兹激光调制及相关的解调检测环节。研究团队使用两台搭载声光调制器的马赫-曾德尔干涉仪，模拟了具备多普勒频移与时延的两条LISA干涉臂。将自参考光学频率梳锁定至提供时钟信号的激光器后，我们分别实现了激光噪声与时钟噪声7个和1.5个数量级的抑制，直至本实验装置的本底噪声水平。基于数值分析，我们进一步证明，基于光学频率梳的时延干涉仪方案的噪声抑制性能可充分满足LISA任务的需求，并留有充足裕度。