Performance limitations of rotationally symmetric nonimaging devices

An upper limit on concentration for any optical device has previously been derived from the conservation of etendue. In this contribution we derive more stringent upper limits for the efficiency and the concentration of rotationally symmetric optical devices that are a consequence of skewness conservation. If the desired source and target have different skewness distributions, then losses or dilution or both will limit the performance of the optical system. We calculate the limiting curve of efficiency versus concentration and provide a design example that is virtually at this limit. We conjecture that even rotationally symmetric problems may benefit from asymmetric optical systems. (C) 1997 Optical Society of America.