Diffractive fan-out elements for wavelength-multiplexing subdiffraction-limit spot generation in three dimensions

Wavelength-multiplexing generation of subdiffraction-limit spots in three dimensions using propagating light was demonstrated and evaluated. Our previous design algorithm [Opt. Express22, 25196 (2014)OPEXFF1094-408710.1364/OE.22.025196] was extended to consider multiple output planes and multiple wavelengths by integrating modulation distributions for individual wavelengths. A diffractive fan-out element that generates subdiffraction-limit spot arrays with two wavelengths on two planes was demonstrated. Spot sizes were reduced to 79% of that of the diffraction-limit spot on average. Numerical calculations showed that seven-wavelength multiplexing is achievable, and the cross-talk suppression conditions are effective for cross-talk suppression between wavelengths.