Abstract
The advent of lossless graded-reflectivity mirrors (GRMs) is now widely recognized as an important headway in the field of optical resonators.1 When used as the feedback output mirror inside an unstable resonator cavity (Fig. 1), a GRM greatly improves the quality of the nearfield by yielding a wide beam with reduced ripples thanks to its tapered edges. In contrast, the more conventional unstable cavity yields an annular output beam with hard-edge truncation and disappointing beam quality for near-field applications.