Second order diffractive optical elements in a spatial light modulator with large phase dynamic range

A study of the diffraction efficiency of a spatial light modulator with a large dynamic phase range is reported. We use a phase-only device that reaches 4π phase modulation depth for the wavelength of 454 nm. This allows operating phase-only diffractive optical elements in the second harmonic diffraction order, instead of in the usual first diffraction order. This type of implementation shows advantages in terms of resolution and diffraction efficiency. Experimental results are reported for blazed diffractive gratings and diffractive lenses.

► Spatial light modulators with large modulation depth are used.
► Phase modulation up to 4π allows working on the second harmonic order.
► 4π phase modulation reduces the resolution exigencies compared to 2π modulation.
► When applied to diffractive lenses, parasite focalizations are considerably reduced.