Method and system for measuring transient time width of ultrashort pulse

A system for measuring a transient time width of an ultrashort pulse in real time, comprising a laser, a beam splitter, a time delayer, a first reflecting mirror, a half-wave plate, a second reflecting mirror, a third reflecting mirror, a first coupler, a fiber, a second coupler, a beam combiner, a lens, a sum-frequency crystal, a time stretching system, an photoelectric detector, and an oscilloscope, wherein

• the laser is configured to generate an ultrashort pulse to be measured;
• the beam splitter is configured to split the ultrashort pulse into two beams, wherein one beam is configured to pass through the third reflecting mirror, the first coupler, the fiber, and the second coupler in sequence to generate the chirped pulse, and the other beam is configured to pass through the first reflecting mirror, the time delayer, the half-wave plate and the second reflecting mirror in sequence, for enabling the two beams to have consistent polarization and time coincidence, and after passing through the beam combiner, the ultrashort pulse to be measured and the chirped pulse are focused by the lens to the sum-frequency crystal;
• the sum-frequency crystal is configured to perform an interaction of the ultrashort pulse to be measured with the chirped pulse, to generate a sum-frequency beam, in which an intensity tag occurs in the chirped pulse after the interaction;
• the time stretching system is configured to perform time spreading on the chirped pulse with the intensity sag;
• the photoelectric detector is configured to detect the spread chirped pulse with the spread intensity sag;
• the oscilloscope is configured to measure a time width τ′ of the spread intensity sag, for calculating the transient time width τ of the ultrashort pulse to be measured according to a formula of τ=τ′/M, where M is an amplification coefficient of the time stretching system.