High-Repetition Rate 2.3-Cycle Shortwave-Infrared Source for Next-Generation Field-Resolved Spectroscopy

Field-resolved spectroscopy has been highly influential in the study of light-matter interactions at terahertz and infrared frequencies, such as the investigation of matter under extreme conditions [1], or accessing fundamentals of quantum mechanics by directly measuring vacuum fluctuations in time [2]. However, conventional electro-optic sampling is limited in its accessible bandwidth by the optical gating pulse duration and phase matching constraints. To overcome these limitations, field-resolved measurements based on small-signal perturbation of nonlinear electron emission have been developed [3]–[6]. Due to the extreme nonlinearity of the electron emission, these methods allow to generate sub-cycle attosecond probes with petahertz bandwidth to measure electric field in amplitude and phase with unprecedented bandwidth. The realization of a universal field-resolved spectroscopy platform based on this method has unique challenges, as it requires high repetition rates for sufficient SNR, few-cycle pulses for the generation of almost isolated attosecond electron bursts, long wavelengths in the NIR to MIR for increased ponderomotive energy, microjoule level energies, and carrier-envelope phase (CEP) stability.