Single-Pulse Phase Spectrum Measurement of Femtosecond Mid-Infrared Pulses at 50 MHz

Mode-locked pulsed lasers are powerful tools across various scientific fields, particularly due to their short pulse duration, high peak power, and high repetition rate. As ultrashort pulses are electromagnetic waves comprising a broad spectrum, measuring and manipulating their phase spectrum is crucial for many applications. For instance, a transform-limited pulse can be generated by the constructive interference of all spectral components, requiring a flat (or linear) phase across the entire spectrum. Measurement techniques such as frequency-resolved optical gating (FROG) and spectral phase interferometry for direct electric-field reconstruction (SPIDER) are commonly used for phase spectrum diagnoses [1], [2].