Time-of-flight spectroscopy with ultrafast all-optical gating

Spectral measurement is crucial in applications ranging from the investigation of matter and its electronic properties to the wavelength-multiplexed routing of optical signals. We propose and demonstrate a spectral measurement technique based on an all-optical approach. The signal spectrum is mapped to the time domain by dispersion in 1 km of fiber and is then optically gated by an intense ultrafast pulse in 10 cm of single-mode fiber. A portion of the signal spectrum can be recovered by sweeping the gate pulse through the stretched signal. Spectral fringes are measured down to the minimum bound for frequency-to-time mapping of 51.5 GHz. Our measurement technique expands the toolbox of ultrafast measurements from the time domain to the frequency domain.