Detection of frequency signal induced by quantum vacuum with optical frequency comb

The properties of the non-trivial quantum state in an all-optical environment come mainly from the higher-order Quantum electrodynamics (QED) effect, which remains one of the few unverified predictions of this theory due to its weak signal. Here, we propose a scheme specifically designed to detect this quantum vacuum, where a tightly focused pump laser interacts with an optical frequency comb (OFC) in its resonant cavity. When the OFC pulse passes through the vacuum polarized by the high-intensity pump laser, its carrier frequency and envelope change. This can be intuitively understood as the asymmetric photon acceleration induced by the ponderomotive force of the pump laser. By leveraging the exceptional ultrahigh frequency and temporal resolution of the OFC, this scheme holds the potential to improve the accuracy of quantum vacuum signal. Combining theoretical and simulation results, we discuss possible experimental conditions, and the detectable OFC signal is shown to be orders of magnitude better than the instrumental detection threshold. This shows our scheme can be verified on the forthcoming laser systems.