Bessel beam

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

Correction of amplitude distortions for truncated Bessel beam and SER estimation for 4ASK

Abstract: We apply amplitude corrections to a truncated Bessel beam that has propagated through turbulent atmosphere modelled by random phase screens. These corrections are realized via transmitting an unmodulated beam in parallel to the one carrying the 4 amplitude shift keying (ASK) modulated message signal. On the receiver side, the amplitude corrections are obtained by dividing the intensity of the unmodulated beam by its free space equivalence. The corrections are then used to restore the amplitude distortions of the beam carrying the 4ASK modulated message signal and in the determination of decision boundaries for the received 4ASK symbols. The success of the system is visually inspected by comparing the received intensity profiles before and after the application of corrections. Furthermore, simulation analysis of symbol error rate (SER) is made, where the proposed set-up is found to be quite insensitive to wavelength difference between the unmodulated and modulated beams. On the other hand, the diff...

THz computed tomography system with zero-order Bessel beam

Abstract: Terahertz (THz) waves can penetrate many optically opaque dielectric materials such as plastics, ceramics and colorants. It is effective to reveal the internal structures of these materials. We have built a THz Computed Tomography (CT) system with 0.3 THz zero-order Bessel beam to improve the depth of focus of this imaging system for the non-diffraction property of Bessel beam. The THz CT system has been used to detect a paper cup with a metal rod inside. Finally, the acquired projection data have been processed by the filtered back-projection algorithm and the reconstructed image of the sample has been obtained.

Quantitative chemical sensing of drugs in scattering media with Bessel beam Raman spectroscopy.

Abstract: Scattering can seriously affect the highly sensitive detection and quantitative analysis of chemical substances in scattering media and becomes a significant challenge for in vivo application of Raman spectroscopy. In this study, we demonstrated a proof of concept for using the self-reconstructing Bessel beam for Raman spectroscopic sensing of the chemicals in the handmade scattering media and biological tissue slices. The homebuilt Bessel beam Raman spectroscopy (BRS) was capable of accurately detecting the Raman spectra of the chemicals buried in the scattering media, and had a superiority in quantitative analysis. The feasibility of the developed technique was verified by detecting the Raman spectra of pure samples in air. Compared with the spectra acquired by the Gaussian beam Raman spectroscope, the performance of the BRS system in terms of Raman spectrum detection and Raman peak recognition was confirmed. Subsequently, by employing the technique for the detection of acetaminophen buried in the scattering media, the application of the new technology in detecting and quantitating the chemicals in the scattering media were underlined, offering greater detection depth and better linear quantification capability than the conventional Gaussian beam Raman spectroscopy. Finally, we explored the potential of the BRS system for chemical sensing of acetaminophen in biological tissue slices, indicating a significant development towards the evaluation of drug in vivo.

Transverse electric (TE) and transverse magnetic (TM) vector vortices in free-space: analysis and experimental generation

Abstract: The experimental generation of vector Bessel beams of different orders with TE and TM polarizations is demonstrated in the optical frequencies domain and in free space by means of a Mach-Zehnder interferometer. For the zero order beams, these modes correspond to the well known azimuthal and radial polarization states, whereas higher order versions become vector vortices, thus carrying orbital angular momentum. The case of the lowest order TE and TM vector vortices, corresponding to a topological charge of l=1, is particularly interesting due to their off-axis location and the non-null intensity at the beam center, unlike the case of topological charges l>1. The polarization and angular momentum properties of these waves are thoroughly analyzed and discussed for different cases. Keywords : Vector beams, vortices, Bessel beams, polarization 1. INTRODUCTION Since they were first introduced in 1987 1 , Bessel beams (BBs) have attracted considerable attention due to their properties of propagation invariance and self-reconstruction, which have found interesting applications in fields like optical trapping and manipulation of microparticles and atoms