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.