- Ultracompact concentrators and illuminators that approach the thermodynamic limit to optical performance can be realized with purely imaging strategies. We explore two-stage reflector systems where each optical surface is tailored to eliminate one order of aberration— the so-called aplanatic designs. The contours are monotonic functions that can be expressed analytically, which are important for the facilitation of optimization studies and practical fabrication. The radiative performance of the devices presented is competitive with, and even superior to, that of high-flux nonimaging systems. Sample results of practical value in solar concentration and light collimation are presented for systems that cover a wide range of numerical aperture.