It is generally accepted that diffractive elements designed for multiwavelength operation require deep surface-relief profiles. We show, however, that thin diffractive elements can be designed to operate with more than one wavelength. A novel, to our knowledge, optimization technique is introduced for this purpose. The maximum phase delay is limited to only a few multiples of 2π, and the element can implement different functions for different wavelengths. Examples with fan-out gratings are discussed.
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