Wavelength tunable laser beam shaping

Laser beam shaping by phase-only transformations, often referred to as field mapping, has for a long time been considered wavelength dependent. In this Letter we outline a simple mathematical argument that shows how the problem may be formulated in a wavelength tunable manner, requiring only a minor adjustment in the observation plane. We verify the theoretical prediction by experiment using the example of a Gaussian-to-flattop-beam transformation, and we show that the shaping is valid across a wide range of wavelengths for a single diffractive optical element.