Two stacked exposures of two different laser modes (upper panel). The image was corrected for background flux. We show that the two different modes are spatially separated as a result of dispersion by the VPH. The 1D spectrum, that resulted from stacking over the vertical axis is shown in the lower panel. The data were normalized to a peak value of one and are shown with a dashed line. The solid grey line denotes two Gaussian fits to the two peaks. These fits were used to derive the positions on the frame and FWHM of the peaks in order to derive the dispersion and resolving power. μ₁ and μ₂ refer to the mean values of these distributions.