1. A method of determining a transient response of a sample, the method comprising: (a) providing a measured magnitude of the Fourier transform of a complex electric field temporal profile of a pulse sequence comprising a first pulse indicative of the transient response of the sample and a second pulse having a stronger magnitude than the first pulse; (b) providing an estimated phase term of the Fourier transform of the complex electric field temporal profile of the pulse sequence; (c) multiplying the measured magnitude and the estimated phase term to generate an estimated Fourier transform of the complex electric field temporal profile of the pulse sequence; (d) calculating an inverse Fourier transform of the estimated Fourier transform, wherein the inverse Fourier transform is a function of time; and (e) calculating an estimated complex electric field temporal profile of the pulse sequence, wherein calculating the estimated complex electric field temporal profile comprises applying at least one constraint to the inverse Fourier transform.