Estimating duration and phase of a single-cycle pulse through measuring light intensity

Studies have revealed that the variation of the normalized photon number of a single-cycle pulse (SCP) with the phase *Φ can be expressed in the form of {1+F*cos(2*Φ)}. Analytical expressions of F-functions in terms of the pulse width have been derived for analytical pulses of different profiles. Considering the fact that, for a train of mode-locked pulses, the phase may change from pulse to pulse, it can be shown that the duration and phase of SCPs can be evaluated with the aid of a square-law photodetector.