Diffraction-free beams for medical imaging

Diffraction-free beams (Bessel and Mathieu beams, x-shaped waves, parabolic beams etc.) have numerous applications in areas as diverse as lidar and remote sensing, spectroscopy and microscopy, and medical imaging (e.g. optical coherence tomography). Instead of using focused Gaussian beams to illuminate the object, these applications take advantage of diffraction-free beams in order to improve the lateral resolution, and increase the depth of field. There are different approaches to obtain such beams that utilize axicons, annular apertures, phase gratings etc. In this work we present a short overview of the state-of-the-art methods for producing diffraction-free beams for application in medical imaging. We show simulation results of several optical designs for tissue characterization, and discuss their advantages and disadvantages.