Temporally super-resolved dispersive Fourier transformation spectroscopy

Dispersive Fourier transformation (DFT) maps the spectrum of an optical pulse into the time domain via chromatic dispersion, enabling real-time, pulse-resolved spectral analysis with a single photodetector. This technique has unlocked new possibilities for single-shot measurements of transient phenomena in physics, photonics, and biological systems. However, its applicability in ultrafast regimes is hindered by temporal aliasing, which arises when pulses are spaced closer than their stretched duration. Here, we introduce temporally super-resolved time-stretch spectroscopy that overcomes this limitation. By storing a sequence of ultrashort pulses—each encoding a unique, non-repetitive spectral event—in an optical cavity and retrieving them sequentially using an asynchronous pulse picker and a DFT oscilloscope, we isolate individual pulses and suppress aliasing. This achieves a three-orders-of-magnitude improvement in temporal resolution. In proof-of-concept experiments, we resolve the spectral evolution of 25 GHz electro-optic comb pulses and distinguish spectra separated by just 3 ps. This technique enables continuous, ps-resolved measurements of non-repetitive spectra and is readily extendable to other DFT-based modalities, including ultrafast microscopy.