An apparatus for performing Raman spectral analysis of a sample is described, comprising a coherent light source, an first optical chain to direct the coherent light to impinge on the sample, a second optical chain to direct the scattered light onto a diffraction grating, and a third optical chain to direct the diffracted light onto detection array. The diffraction grating is a stairstep with a metalized surface, and a plurality of metalized stripes on a flat surface is disposed in a direction orthogonal to the long dimension of the stairsteps. The region between the flat surface and the stairstep is transparent. The zeroth-order fringe is selected by a slit and directed onto camera. The resultant interferogram is Fourier transformed to produce a representation of the Raman spectrum.