Topic
Bessel beam
About: Bessel beam is a research topic. Over the lifetime, 1946 publications have been published within this topic receiving 42264 citations.
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TL;DR: In this paper, the analytical theory for the electromagnetic scattering of plasma anisotropic sphere illuminated by a high-order Bessel beam (HOBB) is investigated using vector wave theory in which electric and magnetic field vectors satisfy Maxwell's equations.
3 citations
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31 Oct 1993
TL;DR: In this article, the propagation of Bessel beams and X waves in attenuating media, like soft tissues, was investigated, and it was concluded that while Bessel beam can be considered as limited diffraction beam in soft tissue, such assumption is not true for X waves, unless when narrowband signals are used.
Abstract: Recently, diffraction limited beams have received increased attention for use in imaging and material characterization. Properties of two particular types, Bessel beams and the X waves, in lossless media have been reported. In medical applications, however, the propagation media are highly attenuative. The authors investigate propagation of Bessel beams and X waves in attenuating media, like soft tissues. In both cases, field of infinite aperture (ideal beam) and field of finite aperture (practical beam) have been studied. Pulsed beams, which are of interest in pulse echo applications, have been included in the authors' studies. Results show that Bessel beams do not spread laterally in attenuating media. In contrast, the X waves spread rapidly in such media. Lateral spreading of wideband X waves is linearly proportional to the depth and the attenuation coefficient. Spreading rate is lower for narrowband beams. It is concluded that while Bessel beam can be considered as limited diffraction beam in soft tissues, such assumption is not true for X waves, unless when narrowband signals are used
3 citations
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30 Nov 2009
TL;DR: In this article, a combination of ultrashort pulse shaping with optical trapping and axicon dispersion compensation is presented, which is the first combination of optical shaping with axicon compensation.
Abstract: Ultrashort pulsed lasers o er high peak powers at low average powers, making them ideal for maximising the e ciency of nonlinear excitation. Their broad bandwidths make it possible to tailor the pulse's temporal pro le for advanced control of multiphoton excitation, techniques known as pulse shaping. This thesis represents the rst combination of ultrashort pulse shaping with optical trapping and axicon dispersion compensation. We construct an optical trapping system which incorporates a 12fs duration pulsed laser, the shortest duration used to date in optical trapping. To achieve 12fs pulse durations at the sample, we must rst eliminate temporal dispersion, which stretches and distorts pulses as they travel through microscope systems. We use the Multiphoton Intrapulse Interference Phase Scan (MIIPS) method to measure and compensate all orders of dispersion in our optical trapping system, verifying 12-13fs pulses at the sample. We use the dispersion-compensated optical trapping system to investigate the e ects of pulse duration on optical trapping. Our theoretical arguments show that trap sti ness is independent of pulse duration. For experimental veri cation, we measure the trap sti ness of trapped 780nm silica spheres with back focal plane interferometry as we change pulse duration by more than an order of magnitude using quadratic pulse shaping. We nd the trap sti ness unchanged within 9%. We also use quadratic pulse shaping to control two-photon uorescence in optically trapped uorescent polymer spheres. Next, we demonstrate two methods for producing selective two-photon excitation in trapped particles: amplitude shaping and 3rd order pulse shaping. Finally, we compensate dispersion in an axicon system, producing a nondi racting ultrashort Bessel beam with controllable dispersion. This forms the basis for ongoing experiments exploring ultrashort Bessel beams in cellular transfection (photoporation), and examining the spatial pro le of the Bessel beam as a function of the pulse's temporal pro le.
3 citations
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TL;DR: In this paper, a novel spatial light modulator based setup that combines the properties of parameter flexibility, long working distance, high throughput and operation on micron-scale is presented.
Abstract: The novel propagation characteristics of Bessel beams have been widely applied to optical manipulation and harmonic generation, and have provided new perspectives on fundamentals of ultrashort laser pulse propagation in nonlinear media. Fully exploiting their many unique properties, however, requires the development of techniques for the generation of high quality Bessel beams with flexible adjustment of the beam parameters. Moreover, long working distances are needed to produce Bessel beams inside bulk samples. In this paper, we report on the development of a novel spatial light modulator based setup that combines the properties of parameter flexibility, long working distance, high throughput and operation on micron-scale. We report both on the general characterization of the beam properties as well as a specific application in surface nanoprocessing.
3 citations
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02 Apr 2004
TL;DR: In this article, a new approach to laser powder sintering and 3D-forming based on Bessel laser beams is presented, where the results of calculations of powder stream impact on bessel beam parameters and powder particles and base heating are displayed.
Abstract: The new approach to laser powder sintering and 3D-forming based on Bessel laser beams is presented. The results of calculations of powder stream impact on Bessel beam parameters and powder particles and base heating is displayed.
3 citations