Application of optical frequency comb in LISA space laser interferometry

Time delay interferometer (TDI) is the baseline technique to mitigate laser phase noises in laser interferometer space antenna (LISA) for gravitational wave detection. Just as important in the TDI scheme is the ability to suppress the local oscillator radio-frequency (rf) noises in the optical heterodyne measurements. This is accomplished currently by sending additional clock tones in the ranging laser and recovering the clock signals with additional heterodyne measurements. We show that the laser and local oscillator noises can be simultaneously cancelled by employing optical frequency combs in which the rf signal phases are coherent with the optical phases. We describe an effort for the experimental demonstration of the optical frequency comb based TDI. The deployment of optical combs eliminates the need for separate ultra-stable oscillators. This approach can be a simpler and more reliable approach than the current modulation scheme. It is applicable to the most generalized TDI combinations.