Abstract
<jats:p>A new method for recording the chirp of a femtosecond IR laser pulse is proposed, based on non-collinear generation of the sum harmonic by a transform-limited IR femtosecond pulse and a pulse with a spectral supercontinuum. This paper presents the time dependences of the instantaneous frequency of an IR pulse with a spectral supercontinuum, obtained from twodimensional distributions of dynamic spectrograms. It is shown that the relative error in determining the chirp of a femtosecond IR laser pulse by the proposed method does not exceed 10%. The presented results can be used in the development of a nonlinear optical phase correlator for determining the phase and time profile of a femtosecond laser pulse in the mid�� IR range.</jats:p>