Bessel beam

About: Bessel beam is a research topic. Over the lifetime, 1946 publications have been published within this topic receiving 42264 citations.

Tightly autofocusing beams along the spherical surface.

Abstract: We theoretically demonstrate different propagation trajectories of tightly autofocusing beams (TABs) along the spherical surface. The generalized expression of the TAB with spherical trajectory is given based on the nonparaxial accelerating Bessel beam. The effect of the spherical trajectory on the focusing performance of the TAB is analyzed. It reveals that the focal field with strong longitudinally polarized component and sub-diffraction-limit focal spot can be further enhanced by shortening the focal length of TAB. Theoretically, the minimum size of the focal spot can be close to 0.096λ2, and the proportion of longitudinal field can go up to 98.36%.

Bessel Beam Radiating System for Focused Transcranial Magnetic Stimulation

Abstract: In this paper, we present an innovative radiating system able to produce a focused treatment for transcranial magnetic stimulation applications. The proposed configuration is based on a non-diffractive Bessel Beam launcher as radiating device. The launcher consists in five concentric planar spiral coils, working at 3 kHz, singularly fed with a proper current amplitude and phase. In this way, a Bessel-like non-diffractive magnetic field distribution can be recreated so that a focused induced electric field inside tissues can be generated. Such peculiar field distribution can find interesting applications for Transcranial magnetic stimulation (TMS), since extremely focused and accurate stimulation can be performed. The numerical results obtained through full-wave simulations show a good spatial resolution and focalization, in term of induced electrical field inside brain tissues at different depths. Such preliminary results suggest the possibility to overcome the single coil performance, encouraging further analysis. Therefore, Bessel beam launchers are potentially good candidates as radiating systems to improve the TMS performance and clinical effectiveness.

Surface acoustic wave quasi-Bessel beams generated by symmetrically tilted interdigital transducers

Abstract: Formation of surface acoustic wave (SAW) quasi-Bessel beams on a piezoelectric substrate through superposition of plane waves generated by interdigital transducers tilted symmetrically about the propagation axis is numerically and experimentally demonstrated. Acting as an axicon, the tilted transducers provide a facile way for quasi-Bessel beam generation. Finite-element method simulations reveal that non-diffracting Bessel beams, whose length and width are 193 and 1.38 wavelengths, respectively, can be obtained on a YX-128∘ lithium niobate substrate for an axicon angle of 15 degrees. The corresponding values for 20 degrees are 146 and 1.05 wavelengths, respectively. For a wavelength of approximately 300 micrometers, transmission spectra show that Bessel beam formation can be achieved at frequencies around 13.3 MHz. Bessel beam is visualized through a thin liquid film of methanol on the substrate. SAW Bessel beams can be utilized in acoustophoresis in microfluidic systems and sensing applications.

On-chip generation of Bessel–Gaussian beam via concentrically distributed grating arrays for long-range sensing

Abstract: Abstract Bessel beam featured with self-healing is essential to the optical sensing applications in the obstacle scattering environment. Integrated on-chip generation of the Bessel beam outperforms the conventional structure by small size, robustness, and alignment-free scheme. However, the maximum propagation distance (Z max ) provided by the existing approaches cannot support long-range sensing, and thus, it restricts its potential applications. In this work, we propose an integrated silicon photonic chip with unique structures featured with concentrically distributed grating arrays to generate the Bessel–Gaussian beam with a long propagation distance. The spot with the Bessel function profile is measured at 10.24 m without optical lenses, and the photonic chip’s operation wavelength can be continuously performed from 1500 to 1630 nm. To demonstrate the functionality of the generated Bessel–Gaussian beam, we also experimentally measure the rotation speeds of a spinning object via the rotational Doppler Effect and the distance through the phase laser ranging principle. The maximum error of the rotation speed in this experiment is measured to be 0.05%, indicating the minimum error in the current reports. By the compact size, low cost, and mass production potential of the integrated process, our approach is promising to readily enable the Bessel–Gaussian beam in widespread optical communication and micro-manipulation applications.

Talbot self-imaging phenomenon under Bessel beam illumination

Abstract: In this paper, we report the results of our theoretical studies on the phenomenon of self-imaging of periodic object under the illumination of zero-order Bessel beam. Our theoretical analysis indicates that the self-images are visible only after the walk-off distance of the Bessel beam used. It is also observed that the self-images bend around the optical axis of the setup. Besides, the present study justifies the importance of the conditions stipulated by Montgomery.