def CalculateRamanResponseFT(self, pulse):
        """
        Calculate Raman response in frequency domain. Two versions are
        available: the first is the LaserFOAM one, which directly calculates
        R[w]. The second is Dudley-style, which calculates R[t] and then
        FFTs. Note that the use of fftshifts is critical here (FFT_t_shift)
        as is the factor of pulse_width.
        """