Electro-optic sampling (EOS) has become a highly versatile, widespread technique capable of performing measurements of optical waves with sensitivity to their oscillating electric field (rather than the cycle-averaged intensity). First demonstrated for free-space terahertz waves thirty decades ago, EOS has recently been extended all the way to the visible spectral region. Importantly, in the mid-infrared (MIR) range, EOS currently holds records for the sensitivity and dynamic range for broadband vibrational molecular fingerprinting.
In their new paper, scientists at the Laboratory for Lightwave Metrology and at Attoworld report the use of EOS as a broadband characterization technique – both in the optical and in the radio-frequency domains – for the temporal jitter of optical waveforms. By recording samples of consecutive broadband MIR waves obtained by intra-pulse difference-frequency generation, the team confirmed ultralow temporal jitter of these trains of waves, reaching even the sub-attosecond range, as well as amplitude stability values on the order of a fraction of a percent. Furthermore, the work demonstrates the ability to characterize waveform jitter in a wavelength-resolved manner by dispersing (that is, chirping) the broadband test wave in time.
The significance of these results is manifold. Firstly, the jitter values reported confirm the outstanding phase stability of ultrashort pulses obtained via intrapulse difference-frequency generation to an unprecedented, sub-mrad level. On one hand this justifies this type of MIR light sources in conjunction with EOS for pushing the frontiers of molecular vibrational spectroscopy toward higher sensitivity and higher speeds. On the other hand, these results present EOS as a field-sensitive measurement method providing more information on waveform jitter than well-established carrier-envelope-phase measurement techniques. These results have also set the stage for attosecond-jitter delay calibration in field-resolved spectroscopy employing two different femtosecond oscillators.
Original publication:
[1] S. A. Hussain, C. Hofer, M. Högner, W. Schweinberger, T. Buberl, D. Bausch, M, Huber, F. Krausz, I. Pupeza, “Sub‑attosecond‑precision optical‑waveform stability measurements using electro‑optic sampling” Scientific Reports 14, 20869 (2024).