High-efficiency diffractive focusing deflecting element

The shape of the diffractive structure of a deflecting kinoform element designed for focusing high-power laser beams with a wavelength of 10.6 µm is studied. Formulas are derived for calculating light losses induced by tilting of the incident beam, diffraction, and technological blurring of the steep slope of the structure. It is demonstrated that the height of the structure varies from the minimum to the maximum value depending on the azimuthal angle. It is found that light loss induced by shadowing due to oblique incidence of the beam is rather low (0.6–1.3%), and that caused by diffraction is smaller by an order of magnitude and can be neglected. The light losses induced by technological blurring of the slope and by deviation of the structure height from the design value (in the case of violation of the azimuthal dependence) can exceed 10%. © 2015, Allerton Press, Inc.