Spectral and angular dependences of the efficiency of three-layer relief-phase diffraction elements of the IR range

Within the framework of the scalar and rigorous diffraction theory based on solving a system of Maxwell equations, saw-tooth relief-phase three-layer microstructures designed for the work with polychromatic radiation of the mid-IR range (3 $\le\lambda\le$ 5 $\mu$m) are studied. The series of effective microstructures composed of different optical materials is extended, and the depths of their reliefs are minimized. The series is extended, in particular, owing to microstructures in which Fresnel losses for reflection from both reliefs do not exceed 10%. This factor, in combination with the relatively low total relief depth, can turn out to be decisive when choosing one or another microstructure for solving a specific scientific or technological problem.