Attosecond-Precision Dual-Oscillator Infrared Field-Resolved Spectroscopy Employing Electro-Optic Delay Tracking

The necessity to precisely determine the delay between ultrashort light pulses is ubiquitous in optical metrology. For pulses originating from the same source, optical-interference-based delay tracking using a monochromatic laser affords precisions of a few attoseconds [1] . However, if the pulses originate from separate modelocked oscillators with detuned repetition frequencies – such as widely employed in dual-frequency-comb spectroscopy [2] and electronically controlled optical sampling (ECOPS) [3] – interferometric delay tracking faces two challenges: (i) the optical phase typically fluctuates independently of the repetition frequency, requiring independent control, and (ii) the interference signal is confined to the time window of the overlap, usually < 1ps.