PI-FROSt characterization of solid-state harmonics with spectra spanning over 2.6 octaves

We present a comprehensive characterization of an ultra-broadband laser field across the visible–mid-infrared (MIR) spectral region. The radiation consists of a series of harmonic fields generated in a ZnO crystal by a long-wavelength, few-cycle driving pulse operating at 100 kHz. The characterization relies on the recently developed Plasma-Induced Frequency Resolved Optical Switching (PI-FROSt) method. In this study, we demonstrate the ability of this straightforward method to characterize, with the same nonlinear architecture, the MIR driving field centered at a wavelength around 3 . 2 μ m , along with all (odd and even) harmonics up to the fifth order. The total spectrum spans over an exceptionally broad bandwidth of 2.6 octaves, ranging from 0.59 to 3 . 6 μ m . All assessments confirm the high reliability and suitability of PI-FROSt for the metrology of over-octave-spanning waveforms, representing an effective solution for characterizing unconventional secondary sources. The field reconstruction provides valuable insights into the generation mechanisms, which can serve as a guideline to support numerical modeling.