Femtosecond Fieldoscopy

Field-resolved detection at near-petahertz frequencies [1] offers exceptional sensitivity, bandwidth, and dynamic range, enabling attosecond temporal and sub-diffraction spatial resolution. In a novel approach termed ‘Femtosecond Fieldoscopy,’ ultrashort excitation laser pulses impulsively excite the in-resonance molecular composition of a sample at near-petahertz frequencies. This interaction initiates vibrational coherence at the trailing edge of the pulses, which decays exponentially at a rate determined by the vibrational dephasing time. The transmitted electric field carries information on the ultrashort excitation pulse, the sample's delayed response over several picoseconds, and a prolonged response from atmospheric gases lasting hundreds of nanoseconds. Field-resolved detection of the molecular response in the time domain and subsequent Fourier analysis of the decaying molecular response yields spectroscopic information with unprecedented sensitivity and dynamic range, achieved by temporally gating the molecular response from the excitation pulse. Enabled by advances in ytterbium laser technology [2]–[6], Femtosecond Fieldoscopy has been shown to resolve overtone, Raman, and combination bands in liquid samples [7]–[9]. Additionally, several approaches have demonstrated to accelerate the technique to real-time sampling [10]–[12] and to extend its capabilities to non-perturbative label-free imaging [13], [14]. In this talk, I present an overview of the recent advancements in this field demonstrated by my group. If time permits, I will conclude with a brief overview of ongoing activities on developing solar lasers and their potential applications in space exploration [15].