A photolithography tool including an optical system for transmitting a beam of radiation toward a substrate is presented. The optical system includes a plurality of calcium fluoride lens elements, optically transmissive of the beam of radiation, each having respective optical axes and imparting a retardance to the beam. The plurality of calcium fluoride lens elements are aligned along an optical path for propagation of the beam of radiation therethrough. Each of the calcium fluoride lens elements includes a cubic crystalline calcium fluoride that is aligned with its [111] lattice direction, or a lattice direction optically equivalent to the [111] lattice direction, substantially parallel with its optical axis. A first calcium fluoride lens element of the plurality of calcium fluoride lens elements is rotated about its optical axis with respect to a second calcium fluoride lens element. The optical system has less than or about 0.015 waves RMS of wavefront aberration.