Comparison of Two Kinds of Pulse Width of Ultrashort Hyperbolic Secant Pulses

The analytical expressions of two kinds of pulse width of ultrashort hyperbolic secant pulses were deduced,i.e.the pulse width at full width at half maximum(FWHM)which was used generally and the root-mean-square(RMS)pulse width which was precise.The comparison of the two kinds of pulse width shows that the FWHM pulse width is different from the RMS pulse width for the subcycle(FWHM pulse width)hyperbolic secant pulses,and the absolute phase affects the pulse width seriously.The RMS pulse width should be used when the subcyle hyperbolic secant pulses is described.