Abstract
The light propagation in the medium normally experiences diffraction, dispersion, and scattering. Studying the light propagation is a century-old problem as the photons may attenuate and wander. We start from the fundamental concepts of the non-diffracting beams, and examples of the non-diffracting beams include but are not limited to the Bessel beam, Airy beam, and Mathieu beam. Then, we discuss the biomedical applications of the non-diffracting beams, focusing on linear and nonlinear imaging, e.g., light-sheet fluorescence microscopy and two-photon fluorescence microscopy. The non-diffracting photons may provide scattering resilient imaging and fast speed in the volumetric two-photon fluorescence microscopy. The non-diffracting Bessel beam and the Airy beam have been successfully used in volumetric imaging applications with faster speed since a single 2D scan provides information in the whole volume that adopted 3D scan in traditional scanning microscopy. This is a significant advancement in imaging applications with sparse sample structures, especially in neuron imaging. Moreover, the fine axial resolution is enabled by the self-accelerating Airy beams combined with deep learning algorithms. These additional features to the existing microscopy directly realize a great advantage over the field, especially for recording the ultrafast neuronal activities, including the calcium voltage signal recording. Nonetheless, with the illumination of dual Bessel beams at non-identical orders, the transverse resolution can also be improved by the concept of image subtraction, which would provide clearer images in neuronal imaging.
Highlights
Light propagates rectilinearly and experiences diffraction in daily life [1]
We started from the fundamentals in non-diffracting beams, followed by the generation and biomedical applications of the nondiffracting beams
In terms of the application aspect, we mainly focus on biomedical engineering, including fluorescence microscopy, two-photon microscopy, label-free Raman microscopy, and optical non-invasive manipulation of biological cells
Summary
Light propagates rectilinearly and experiences diffraction in daily life [1]. The light diffraction is the consequence of the violation of the rectilinear propagation. The diffraction is defined as any deviation from rectilinear propagation [1]. Strong diffraction appears when the transverse dimensions are comparable with the wavelength. Strong diffraction is more pronounced for long waves such as water or sound waves, while being less appreciable in optics. The diffraction is in charge of the beam divergence in the free-space propagation and propagation into the shadow region [1]. Diffraction, as a natural wave property, features the nonhomogeneous distribution in transverse intensity. Durnin has introduced the controversial term “non-diffracting beam” into optics in 1987 [2, 3]. The non-diffracting beams have been intensively investigated in both theory and experiment.
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