Development of Attosecond Cross-Correlator for Evaluation of High-Harmonic Generation

It has been a challenge for time-resolved quantum physics to watch the ultrafast electrons transition from one constituent to another or the ejection of electrons from an atom or molecule. These higher-energy processes happen at attosecond timescales are increasingly relevant to a broad range of science and technology for the applications of quantum electrodynamics. Thus, development of a new capable time tool is in need. In this study we introduce an attosecond cross-correlator system for quantum electrodynamics namely Hyperspectral Attosecond Quantum X-correlator (HAQ-X). The system is based on a balanced optical cross-correlator (BOC) by analyzing a pair of femtosecond laser pulses with one encoded by high-harmonic frequency comb generated due to optically pumped quantum materials. Due to the work of BOC the sum-frequency intensity differences after double-path through nonlinear crystal, the amplitude differences indicate the temporal delay of the two wave packets. To measure physical phenomenon with HAQ-X, we are investigating one type of ultrafast electronic dynamics that evolves with electron ionizations in a strong field leads to high-harmonic generation (HHG) process. The frequency comb will have attosecond temporal features to challenge our capabilities. Capturing temporal information of HHG can provide a new understanding of HHG via quantum mechanics. This could lead to new possibilities of generating paired photons in a strong field or entanglements at high photon energy level. Theoretical modeling of the HAQ-X system is developed to determine the temporal sensitivity, by applying the properties of known quantum material that generates high order harmonics such as Single- or double-layers Graphene, ZnO, MoS₂, and Cd₃As_2. Simulation results of HAQ-X system outputs a 0.02 to 10 pW/attosecond sensitivity level. The operation mechanism of HAQ-X provides resilience in noise and time jitter, makes it a robust and cost-efficient time tool that allows us to analysis ultrafast electrodynamics and unveil new physics.