It is convenient to measure picosecond pulse width by using intensity autocorrelators, such as pulsecheck of Germany APE Company and Femtochrome of America. Of course, you can also say that you have measured the time domain waveform of the pulse. There are many options for measuring femtosecond pulse width, and the above two can also be used. There is also interference autocorrelation, such as Femtometer of Femtolasers in Austria. In addition, FROG and SPIDER can also be used to measure the spectral phase of ultrashort laser pulses more accurately and in detail. Knowing the spectral phase of laser, we can reconstruct the time-domain waveform of laser pulse and know the pulse width. In other words, if we know the spectral phase of laser, we will know its chirp characteristics.

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