Achromatic negative index lens with diffractive optics

In this paper, achromatization of a negative index lens is achieved by introducing the diffractive optical elements (DOEs) into the negative index lens. The diffraction efficiency of the negative index material (NIM) DOEs is deduced based on the special propagating laws and imaging properties of negative index lenses, and the expression for microstructure height is given. As an example, an achromatic refractive–diffractive negative index lens with 150 mm focal length and 15 mm entrance pupil diameter is discussed from wavelength 0.848 μm through wavelength 0.912 μm to wavelength 1.114 μm. According to the deduced expression for the NIM DOEs, the diffraction efficiency is calculated, and the diffraction efficiency curve is fitted by interpolation. (paper)