An optical system (31) with an input optical source (33) for projecting an input beam along an optical axis and an optical element (37, 43) which creates a cone refracted beam (41) from the input beam (35) then reconstructs the input beam (49). The optical element may comprise a first cone refractive element (37) which creates a cone refracted beam and reconstructs the beam using a reconstructing optical element (43) to apply a phase shift to the cone refracted beam. The optical system may be used to form a laser or a gain medium for a laser.