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2D Waveguided Bessel Beam Generated Using Integrated Metasurface-Based Plasmonic Axicon
摘要： Near-field imaging of the propagation of a diffraction-free Bessel-type beam in a guided wave configuration generated by means of a metasurface-based axicon lens integrated on a silicon waveguide is reported. The operation of the axicon lens with a footprint as small as 11μm2 is based on local engineering of the effective index of the silicon waveguide with plasmonic nanoresonators. This generic approach, which can be adapted to different types of planar lightwave circuit platforms, offers the possibility to design nano-engineered optical devices based on the use of plasmonic resonators to control light at the nanoscale.
关键词： Bessel beams,optical metasurfaces,Silicon photonics,surface plasmon resonances,Axicon
更新于2025-09-23 15:19:57
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Design of a laser-based autofocusing microscope for a sample with a transparent boundary layer
摘要： This study proposes a new type of autofocusing microscope. The microscope was combined with a polarized beam-splitting system and an image-processing program to overcome the complex signals generated when focusing on a transparent boundary layer. The polarized beam-splitting system divides a source laser beam into four parallel beams using a birefringent crystal. It also uses an axicon lens to focus individually on different positions of the sample surface when light is incident on the objective lens to observe multiple-spot defocusing information simultaneously. The transparent boundary layer exhibits intricate signals when a sensor detects laser spots. Therefore, an image-processing program is proposed to filter unnecessary signals for calculating the evaluation function and driving the motor, which enables a focused view of the test sample to be attained conveniently. To prove the feasibility of the proposed autofocusing microscope, a frame was developed using a simulation software for observing the initial characteristics of the microscope and for conducting a qualitative analysis. Moreover, the image-processing effect on the sample was tested to determine whether the aim of the study was achieved. The experimental results matched suitably with the simulation results, which indicates that the proposed autofocusing microscope can solve the problem caused by the transparent boundary layer and can achieve a high focusing accuracy within a short focusing time.
关键词： polarized beam-splitting system,birefringent crystal,autofocusing microscope,transparent boundary layer,image-processing program,axicon lens
更新于2025-09-19 17:13:59
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Generation of Droplet Quasi-Bessel Beams Using a Semiconductor Laser
摘要： A method for generation of droplet quasi-Bessel beams using a conical lens with a rounded tip is demonstrated. The study of the longitudinal distribution of the intensity of the obtained quasi-Bessel beam showed that, due to the interference of two wavefronts that occurred as the generating beam passed through the rounded axicon, periodical intensity pulsations that looked like “drops” of light occurred in the resulting beam. These light beams can be used for micromanipulation of biological objects and in super-resolution microscopy. The application of an axicon with a rounded tip for generation of a droplet beam allows considerable simplification and miniaturization of the experimental setup, which paves the way for multiple practical applications.
关键词： axicon,droplet beams,Bessel beams,semiconductor laser
更新于2025-09-16 10:30:52
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Kummer laser beams with a transverse complex shift
摘要： Here, we study asymmetric Kummer beams, whose complex amplitude is proportional to the Kummer function (a degenerate hypergeometric function). These beams are exact solutions of the paraxial equation (Schr?dinger-type equation) and are obtained from the conventional symmetric hypergeometric beams by complex shift of the transverse coordinates. On propagation, the asymmetric Kummer beams change their intensity weakly and rotate around the optical axis. These beams are an example of vortex laser beams with a fractional orbital angular momentum (OAM), which depends on four parameters: the vortex topological charge, the shift magnitude, the logarithmic axicon parameter, and the degree of the radial factor. Changing these parameters, it is possible to control the beam OAM, continuously increasing or decreasing it.
关键词： asymmetric laser beam,orbital angular momentum,optical vortex,logarithmical axicon,Kummer function,hypergeometric function
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Generation of Vector Bessel Beams and their Application for Laser Microprocessing of Transparent Materials
摘要： Bessel beams are perfect candidates for laser microprocessing of transparent materials due to generation of high aspect ratio micro voids [1], and ability to control micro crack formation enables to efficiently cut them [2, 3]. The crack propagation direction is controlled by inducing asymmetry to beam profile [3], and allows ultra-fast glass cutting over non-straight lines. The laser-matter interaction of various nondiffracting beams is heavily investigated and their utilisation for laser microprocessing is soon to be expected. Vector beams that are more exotic than scalar counterparts and can have additional beneficial properties for micro-manufacturing of materials. For instance, vector Bessel beam has a doughnut shaped intensity profile with complex spatial distribution of polarisation and can be de-composed to two transverse polarisation intensity components [4]. In this work, we examine generation of vector Bessel beams using an axicon and an s-plate (Workshop of photonics) – radial polarization converter [5]. The s-plate allows generation of azimuthally or radially polarized beams while axicon converts it to nondifftracting Bessel vector beam. The polariser was used to separate its orthogonal polarisation components (Fig. 1). The proposed approach to generate these beams is beneficial for high energy beam systems because s-plate withstands ultrashort (fs-ps) high power pulses. To investigate their applicability to transparent material micro-fabrication we performed microprocessing of a glass with vector Bessel beams and were able to induce high aspect ratio volume modifications and micro cracks in transparent materials. Vector Bessel beams produces cylinder shaped material modifications of glass (Fig 2 a)) while the use of single polarisation component generates two parallel needle like material modification (Fig. 2 b)). By elongating the pulse duration to few ps we have observed micro crack formation extending perpendicular to the beam propagation direction and to two intensity peaks. (Fig. 2 c)). The produced modifications are investigated to increase the laser microprocessing quality and speed.
关键词： Bessel beams,laser microprocessing,transparent materials,axicon,vector beams,s-plate
更新于2025-09-12 10:27:22
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Detecting the Extremely Small Angle of an Axicon by Phase-Shifting Digital Holography
摘要： Axicon is an optical element that can be used to produce high-quality Bessel beams efficiently. In general, the smaller the base angle of the axicon is, the longer the diffraction-free distance of the generated Bessel beam will be. Therefore, axicon with an extremely small base angle is important for the generation of Bessel beam. However, the measurement of an extremely small base angle is a challenge. Here, we applied the phase-shifting digital holography in the measurement of axicon angle. The errors of the three measured axicons with base angles of 0.5°, 1°, and 1° were 1.94%, 4.43%, and 1.63%, respectively.
关键词： digital holography,axicon,phase measurement,phase shift
更新于2025-09-11 14:15:04
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Packaged Negative Axicon Optical Fiber Probe and Bessel Beam Interferometry for Refractive Index Measurement of Hazardous Liquid Samples
摘要： In this work, we demonstrate the packaging of an optical fiber negative axicon probe generating Bessel beam and its application in the measurement of refractive index (RI) of hazardous liquids. The negative axicon probe is placed inside cascaded capillary tube capped with a glass coverslip of RI ~1.52 and thickness ~0.15 mm. The packaged probe, connected to a broadband source through an optical circulator, is dipped in different hazardous liquid samples. The reflected light from the air-glass as well as the glass-liquid interface couples to the negative axicon probe and interferes with the reference beam generated at the air-negative axicon interface. The interference spectra recorded in a spectrometer through the circulator are analyzed applying Fast Fourier Transform (FFT). The FFT helps to separate and measure powers reflected from the different interfaces which are used to solve the Fresnel equation for estimating the RI of hazardous liquid samples, such as HCl, H2SO4 solutions. The resolution achieved is 1*10-4 ± 0.0005. The probe can be useful to measure RI of liquid samples remotely and in hazardous environmental condition.
关键词： refractive index,Bessel beam,Negative Axicon,optical fiber,hazardous liquid
更新于2025-09-11 14:15:04
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Off-Axis Vortex Beams Diffracted by a Circular Grating
摘要： We examine vortex beams shifted from optical axis and diffracted by a circular grating or a binary diffractive axicon. We consider the diffractive axicons with a numerical aperture equal to 0.95 and 0.5. Modelling of diffraction is numerically realized in the 3D-model by the finite difference time domain (FDTD) method.
关键词： diffractive axicon,circular grating,FDTD,off-axis vortex beams
更新于2025-09-09 09:28:46
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Tunable depth of focus of acoustical pupil masked Soret Zone Plate
摘要： In acoustical lenses both resolution and depth of focus are determined by diffraction and the smaller the lens aperture the worse the resolution and the greater the depth of focus. Diffraction-limited resolution has a Soret Zone Plate, but a long depth of focus has an axicon. Nevertheless, these are two different devices each of which requires its own independent design. In this paper we have shown that the transition from focusing to a diffraction limited spot to a quasi-diffraction free beam can be realized in the same focusing device without changing its topology. It has been shown that using a classical planar Soret Zone Plate lens made of a concentric array of circular aperiodical rings with an amplitude pupil mask placed closely to the surface of lens allows to form a quasi-Bessel beams under specific conditions, part of a diffracted wave collimates, producing an elongated focus. Experiments are performed in water tanks in order to verify the simulation results. Experimental verification shown that the depth of focus of a pupil-masked Soret Zone Plate increases 1.63 times and resolution increases 1.2 times (with minimal beam waist about of 0.67 of wavelength and depth of focus about 5.72 of wavelength). By dynamically controlling the size of the amplitude pupil mask, it is possible to quickly control the depth of focus of an acoustic lens.
关键词： ultrasonic lens,acoustic bessel beam,axicon
更新于2025-09-04 15:30:14