Spectrally filtering at least one input beam includes: dispersing spectral components of at least one input beam at respective angles in a spectral plane; changing at least some of the angles of the propagation axes of the dispersed spectral components so that a plurality of the spectral components reflect from a single reflective surface; and tilting the reflective surface to select at least one and fewer than all of the received spectral components to be directed to an output spatial mode.