Topic
Bessel beam
About: Bessel beam is a research topic. Over the lifetime, 1946 publications have been published within this topic receiving 42264 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: Experimental and simulation results of using a segmented deformable mirror to generate zero- and higher-order Bessel beams that have a controllable transverse and longitudinal shape are reported.
Abstract: Bessel beams with tunable spot size are desirable for many applications such as laser material processing, optical trapping, and imaging. In this paper, we report experimental and simulation results of using a segmented deformable mirror to generate zero- and higher-order Bessel beams that have a controllable transverse and longitudinal shape. The tilt angle and piston position of the mirror segments are optimized to recreate the phase structure of a reflective axicon. Zero-order Bessel beams are generated at various beam converging angles, and their core diameter, peak intensity, and depth-of-focus are found to agree with the calculated results. By applying a phase ramp along the azimuthal direction, the first-order Bessel beam is generated with the characteristic annular shape. Because deformable mirrors have low absorption and dispersion and operate at a fast frame rate, they are a promising candidate for spatial beam shaping of high-power ultrafast lasers, which are used in material processing applications.
18 citations
TL;DR: This work generated partially coherent Bessel and Gaussian beams using a spatial light modulator and studied the speckle pattern intensity in propagation after some speckles were blocked, demonstrating that these partially coherent beams are unexpectedly robust against scattering by objects.
Abstract: It is well known that coherent Bessel beam, a nondiffracting class of beam, possesses the ability of self-reconstructing or self-healing in the presence of obstacles. Here, we generated partially coherent Bessel and Gaussian beams using a spatial light modulator and studied the speckle pattern intensity in propagation after some speckles were blocked. We demonstrated that these partially coherent beams are unexpectedly robust against scattering by objects, overcoming the coherent Bessel beam and remaining independent of any special class of partially coherent beams.
18 citations
TL;DR: A tomography approach for scanning fluorescence microscopy which allows recording a volume image in a single frame scan and reconstructed using inverse Radon transforms combined with convolutional neural networks (U-net).
Abstract: Light microscopy on dynamic samples, for example neural activity in the brain, often requires imaging volumes that extend over several 100 µm in axial direction at a rate of at least several tens of Hertz. Here, we develop a tomography approach for scanning fluorescence microscopy which allows recording a volume image in a single frame scan. Volumes are imaged by simultaneously recording four independent projections at different angles using temporally multiplexed, tilted Bessel beams. From the resulting projections, three-dimensional images are reconstructed using inverse Radon transforms combined with convolutional neural networks (U-net).
18 citations
TL;DR: In this article, a zero-th order quasi-Bessel beam is formed with an axicon lens made from high density polyethylene (HDPE) for terahertz imaging.
Abstract: Terahertz (THz) imaging is promising for nondestructive evaluation, since many optically opaque dielectrics are
transparent to THz waves. Conventional THz imaging systems employ focusing elements such as spherical lenses and
off-axis parabolas, but their fixed focal length produces an inherent trade-off between lateral resolution and depth of
focus. Furthermore, image quality suffers when imaging objects located inside a dielectric medium. The air-dielectric
interface introduces significant spherical aberration that degrades spatial resolution. Bessel beams are known to produce
a small spot size over a large depth of focus. The contribution of our work is two-fold: (1) We demonstrate THz imaging
with a significantly improved depth of focus using a zero-th order Bessel beam produced by an axicon lens. (2) We also
demonstrate, for the first time to our knowledge, that Bessel beams experience reduced spherical aberration when
imaging objects embedded in a dielectric medium. Imaging experiments are performed with a time-domain THz system,
where a zero-th order quasi-Bessel beam is formed with an axicon lens made from high density polyethylene (HDPE).
The HDPE axicon has a 50 mm diameter and an apex angle of 120 degrees. Point spread function (PSF) measurements
confirm that lateral resolution is maintained over a 25 mm depth of field in air. The same lateral resolution is achieved
over a 35 mm range inside a HDPE substrate. Needle objects embedded inside a thick HDPE substrate are imaged with
high spatial resolution. Image contrast is significantly improved by digital filtering to reduce sidelobe levels. These
promising results suggest that Bessel beams are well suited for terahertz nondestructive imaging of thick dielectric
objects.
18 citations
TL;DR: These lenses could provide an attractive alternative to parabolic reflectors for terahertz imaging applications where a large depth of focus and/or efficient and controllable coupling of radiation onto a small target are desirable.
Abstract: We report the generation of Bessel beams using polytetrafluoroethene conical lenses and a quantum cascade laser emitting at 2.8 THz. The formation of a central beam spot that retains its size over distances exceeding the characteristic Rayleigh range is demonstrated, and the power transport properties of these beams are compared with those obtained using parabolic reflectors. These lenses could provide an attractive alternative to parabolic reflectors for terahertz imaging applications where a large depth of focus and/or efficient and controllable coupling of radiation onto a small target are desirable.
18 citations