Laser apparatus comprises a laser assembly (30) for producing light having multiple lobes in its far field intensity pattern. A light feedback element (37) forms a resonant external cavity with the laser assembly (30) for returning to the laser assembly light (34) derived from a first lobe of the light produced by the laser assembly, an output beam (35) being derived from a second lobe. The light feedback element has a reflective surface (38) for reflecting back to the laser assembly light incident on the reflective surface. A spatial filter restricts the transverse modes of the feedback light to one or more selected transverse modes, and includes a masking element (41) positioned between the reflective surface and the laser assembly. The spatial filter is formed by a pair of opposed edges (39, 40) comprising an edge (39) of the reflective surface and an edge (40) of the masking element (41).
