Shaping diffraction-free Lommel beams with digital binary amplitude masks

Here, we report on experimental observations of various Lommel modes that possess distinct diffraction-free behaviors. The binary amplitude masks are designed to accurately encode the complex field information with the superpixel method. Then, the generation of the desired beams is demonstrated with these binary patterns projected onto the digital micromirrors device (DMD). Remarkably, we find that the field distribution and orbital angular momentum can be continuously engineered by tuning the beam parameters. Furthermore, the shape-invariant feature of such beams is verified by their far-field ring-like structures. Our observations are in good accordance with the theoretical predictions, and our methods may find potential applications in optical guiding and imaging. Moreover, apart from the DMD, the binary amplitude hologram can also be presented with well-fabricated elements, and thus, our method will also enable new applications for surface plasmon polaritons as well as electron beams. (C) 2015 Optical Society of America