Harmonic kinoform lens: diffraction efficiency and chromatism

Sawtooth microstructures with a relief depth significantly exceeding the central wavelength of the working spectral range are studied within the scalar and strict diffraction theories. The possibility of maintaining high diffraction efficiency, irrespective of the working spectral bandwidth and at allowed angles of incidence, which can reach 45$^{\circ}$ or more, is shown. It is also shown that the chromatism of such lenses is controlled in a very wide range and can be less than that of the lightest crown glasses.