The ability to resolve the complete electric field of laser pulses from terahertz to mid-infrared spectral ranges has enriched time-domain spectroscopy for decades. Field-resolved measurements in this range have been performed routinely in ambient air by various techniques like electro-optic sampling, photoconductive switching, field-induced second harmonic generation, and time stretch photonics. On the contrary, resolving the electric field of light at the near-infrared spectral range has been limited to attosecond streaking and other techniques that require operation in vacuum. Recent advances are circumventing these shortcomings and extending the direct, ambient air field detection of light to petahertz frequencies. In the first part of this letter, recent field-resolved techniques are reviewed. In the second part, different approaches for temporal scanning are discussed, as the temporal resolution of the time-domain methods is prone to temporal jitter. The review concludes by discussing technological obstacles and emerging applications of such advancements.
Large-scale draw tower gratings (DTG) are interrogated using incoherent optical frequency domain reflectometry ( iOFDR) w ith h omodyne f requency conversion. We successfully demonstrate quasi-distributed temperature sensing with a total number of N = 500 DTGs.
We propose a concept for Raman distributed temperature sensing based on L-band excitation and C-band Anti-Stokes detection. The concept is demonstrated by interrogation of 1500 m fiber with incoherent optical frequency domain reflectometry.
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