Ultrafast autocorrelator based on broadband radio frequency spectrum analyzer

Autocorrelator, as a pulse measuring equipment, can effectively characterize pulse width and pulse waveform with high resolution. Limited by the refresh rate, conventional autocorrelator are incapable of capture the ultrafast processes of pulses, such as soliton transitions. In this paper, we proposed an ultrafast autocorrelator based on broadband radio frequency (RF) spectrum analyzer. The RF spectrum under test is firstly transformed to the continuous wave via the cross-phase modulation. Then the RF spectrum is mapped to the temporal domain through time stretch and finally measured by a real-time oscilloscope. The ultrafast autocorrelation trace is obtained from the inverse Fourier transform of the mapped RF spectrum. With the 60-GHz detected bandwidth of the photodetector adopted, the simulated ultrafast autocorrelator achieves the measurement rate of 50 MHz, the resolution of 300 fs, and the measuring window of 600 ps.